If BW2 includes a G3 remake/extra region, I won't complain. It'll actually be cool。 Never played G3. I would hope for new, homage tutors, not the exact same ones.
A HG/SS-style remake of G3, though, would be pretty disappointing.
Personally I wouldn't mind a whole new (preferably post G6) game that took advantage of the 3ds's amazing space. Give me G1->G4 by boat, back to G2 w/ 3 different ribbon-granting elite 4s (singles, doubles, triples). Include lots of spotpass/mystery gift options.
Then again I'd like in-game cloning options (w/o EVs? Make 'em work for it?), unlimited rebattles of NPCs, and "random catch" teams for bugcatchers/fishers, and normal teams that level up every time you defeat them normally.