That has already been done; the current launcher, which was released earlier this year, is a native executable, no doubt written in C++, which is why you don't even need to install Java in order to run it (the bundled runtime is only used by the game itself):
"No longer requires Java", "interface redesign". Sure sounds like it (I have no idea what Win10 looks like).
You are correct the launcher is a C++ application. The Win10 version does not actually have a seperate launcher, is just a menu/options screen built directly into the game. The [Play] button allows you to Manage Worlds, Add Friends, and Connect to Servers. Manage Worlds allows you to create your own world and play it as single player or multiplayer, add options like resource packs and behavior packs (plugins maybe?) that you can buy.
So in just a few mouse clicks you can be up and running with your own server private and invite players to join, including console players. Or you can create a Realms server and make it public or private. The public servers already on the list look remarkably like some of the large Java based servers that host multiple worlds with different server modes and minigames.
I started playing Minecraft on the XBox MC version equivalent to 1.4 and switched to the PC version after about 6 months. NEW MC players that come from the XBox are unlikely to take that same path, but instead move up to Win10. Where they can still play with their friends, have built in chat, friends list, and many of the benefits of the Java Edition in an easier to use package.
There was nothing listed under the behavior packs page, so that is likely an indication of things to come. So the original question, will Win10 ever connect to Java Edition? I've changed my mind and say probably not. Will the Java Edition ever connect to Win10 servers? Maybe, but I think it's more likely that the Java Edition will gain Win10 like features as long as MS can see a way to monetize those features.