I created a new world, and it is mid-ocean, with little islands everywhere, I don't see a village or think a village would spawn out here... The fun part is that I spawned next to a Mushroom Fields biome, the first I've ever seen in survival.
My question is this:
When the new update drops for Java, could I use the Re-Create option in world creation in order to have the Pillager update, so that if there ARE any villages or things out here, they would be able to be attacked and so on? I want to keep my new world, but I also want it to update when it comes out. Am I making any sense?
Recreate doesn't apply itself to existing worlds. Instead, it makes a brand-new world instance with the seed (and probably some of the world type options) inherited from the original world. Specific playtime info like player inventory, regional difficulty, and advancements and statistics are reset back to factory defaults because technically this is a brand new world.
Seed determines structure placement, and minecraft version determines what the seed generates. It's always possible that a seed used in an older version (1.13) will produce different results in a newer version (1.14), but it probably won't in this case. There will be some minor differences due to RNG fluctuations--a different set of caves generated, more or less M-variants in different biomes (the M part is a flag set for the biome, and therefore is probably determined by a random roll), probably different sub biomes (ie, sunflower plains instead of flower fields), and so on.
No structures specifically require Mushroom Island as a location, and other than abandoned mineshafts, spawner dungeons, and strongholds (which have no biome restriction at all) there won't be any structures in this biome. I dunno if this applies to pillager outposts, but if they have to be located near/in biomes that villages can spawn in then you likely won't see any from your mushroom island. You might see some 1.13 ocean structures, but if this is already a 1.13 world and you've seen for yourself there are no structures in the water then this is unlikely to change when you update to 1.14.