Thereby, cobblestone is the oldest block together with grass. You could even consider grass the oldest to see, because it is the first block you see when starting the most early version of Minecraft. And the texture of grass has, for so far I know, never changed, except for loosing the full grass on sides in the pre-classic versions (biome specific colors do not count, because it is still only just one texture). So changing the texture of grass, that would be something special to see.
Necessarily, 1.13 won't be a "big" update. It might even be the last update. Microsoft said they would abandon PC Minecraft, and go onto Console and PE. So who knows happens after 1.13?
No, it is not going to be the last update. Mojang will continue to release updates for Java Minecraft. 1.13 will indeed more be a maintenance update, so I understand, to polish the game and to squash some persistent bugs. But it will not be the last one.
This actually doesn't make sense. If the current artstyle is a mixture of different texture work in the first place, why would this matter? Mojang has constantly added new textures that didn't match the "old style". Did people specifically re-texture Jeb's work when it was clearly different from Notch's style? Not really.
More importantly, what exactly is the "old artstyle" when exactly 7 people have made textures, each with their own different style?
Currently it doesn't make sense indeed, but I understood that they actually want to adress exactly this problem with the new texturing. So if you then still use the old mishmash textures, they will then probably clash with the new concordant textures.
With more updates and new textured features coming, the new unanimous style will of course more and more prevail in your game and the old textures from your resource pack will become more and more weird exceptions.
Resource packs resembling the alpha or beta textures, do indeed mostly not retexture new features in the mentioned styles. And that gives strange results, with very bright grass and sharp contrasted cobblestone next to much more subtile stonebricks and more dark hardened clay.
Some people will be fine with that, but qua style it can be quite a disaster to not properly retexture new features in the style you are going for, and those nostalgic packs are proving that pretty much for me.
honestly though, that is REALLY insignificant to something you can simply add yourself by simply extracting the resources already downloaded on your computer from the Minecraft jar. You dont need to download a resource pack anywhere. You just need to select a version of minecraft with the old textures and extract them and make a resource pack out of it.
Until new updates with new features are coming out. Then you have to texture all those features for yourself in the old style, or accept that the textures of most new features will clash qua style with your old ones.
Because from the moment the new textures are implemented, every single new feature, from mobs to blocks, will be textured in the new style.
The issue I have with this is that especially the emerald block have a really clear light source. This makes it look like an actual jewel but it also makes it look weird when your light source isn't actually coming from that point. For instance in this picture:
The white triangles on the floor and ceiling don't match up and it's annoying me to death. I like the idea of making them look like actual jewels but I dislike the fact that they seem to be trying to make the side "stick out" without it actually sticking out. It looks off to me.
That is indeed a legit point you have. The problem however is when you remove or dim that glinster too much, the emerald would look much more dull and not realy as the shiny stone it is. You can see that now already with the current texture. It is quite bland and not very useful as juwel and for many players also not as real building stone.
With placing the glinster in the centre, like in the (current) glass texture, you just replace the problem to the centre in this case. And the light engine of Minecraft is, for so far I know, not capable to let textures interact with the light in such a way, that the textures do properly glinster.
One must then draw more contrast in the texture for a more in depth block, but too much contrast doesn't look good in large scale use. And the texture would still then not look really like a glinstering stone, but more like a stone with deep carves.
So it is pretty difficult to make a shiny texture without clashing too much with light sources and contrast issues. You will always find situations where even a very beautiful texture suddenly doesn't really fit, but that is something you will find with almost every texture in Minecraft.
The texture artist must then take into account where the block is probably going to be mostly used for. A normal brick will be used often in large walls, roofs, etc., so it needs a generic, easy on the eye texture with not too many specific details or patterns.
But a jewel block will mostly be used for small accents and decoration. So it doesn't have to be made fit for large buildings (with complicated light maps) and thus can have some special, unique textures.
If someone then still decides to build Emerald City, (s)he can then always combine the emerald blocks with other fitting blocks, to prevent the mentioned problems. And he will then indeed face maybe some restrictions, but that is for the most part the charm of Minecraft anyway. If you want to build weird, unusual things, well, the challenge is then on you.
So I don't see a problem with the juwel textures of diamond and emerald. I think it is good that textures are getting more character and depth. It will maybe restrict you a little more in your designs, but when used the proper way, they will make your buildings and decorations actually look much better and much more lively.
Together all of Minecraft's textures makes an artstyle that makes the game unique. If you change the textures, you kinda lose this feeling.
As I see, they are not really changing the artstyle, but only the amount of details in every textures. They also, so I see, try to make them more realistic. Raw obsidian in real life for example looks like this:
So they try now, as I see, to make the Minecraft obsidian more rocky then it is now, especially because Minecraft obsidian is much more sturdy then real obsidian.
They also try to make blocks of noble metals, like diamond and emerald, actually look like huge square juwels. In my opinion the shown emerald texture and color is spot on, making it much more feasible to build for example the emerald city. Also the new diamond block looks much more as an actual huge diamond then just a plain cyan block.
So I'm just very curious about the new textures and I just hope they will make the game just more pretty and unified qua art and style. However, I also think it would not be a bad idea to change the resolution to 32x32 pixels, because then some details will look just better and sharper and it gives more freedom to add even more details. But I don't think that is going to happen; I guess it would change the sight of the game too much.