Sounds like there is a rumor going around that large monitor support and UI scaling support will be added to Terraria as part of 1.3.5. I'm hopeful. The XNA alternative that is used on the Mac and Linux ports doesn't have the XNA texture size restriction that limits them to 2048x2048 and lower resolutions on PC, so if they just use the same codebase for Windows, all will be good.
So, if the number one feature of RomTerraria gets put as a feature of the main game, what will happen with RomTerraria going forward? I don't know. In the past, the main feature of RomTerraria was the minimap, and that was brought in.
If I had to guess, assuming nothing blows up with the retail release, RomTerraria as it exists will be retired completely come the release of v1.3.5. I'll likely take a break from Terraria modding for a couple of months, then come back with something new.