I don't know just how long 3.0 will be, but if you play 2.2.0, I think 3.0 will feel like a whole new game. :)
I tried instant text originally, but it made some lines not appear at all—text that auto-scrolls, like certain important messages in battle, would just be overwritten. I'll reconsider it, though; maybe that's fixable, or I can just warn players about it.
Still playing around with which tiles to change. I think Pokémon Centers will have the same layout in both regions, since they did in GSC and HGSS.
Edit:
Yes it would. I'm not prepared to invent a whole region worth of content, but Mateo's planning to eventually include the Orange Islands in Red++ (I think), so since that's in the same universe as Polished Crystal we could probably cooperate on that. But that's a long way away; both Red++ and Polished Crystal have 3.0 versions in development focusing more on implementation changes than on new content.