It would be great if there were an announcement sometime this year. I really thought there would've been something by now.
As far as the next game's location, I'm pretty much up for anywhere really. It would be nice to get a new start. A huge map with all kinds of unfamiliar locations to explore. I know it's already been said and I agree, exploration is part of the fun. With III, VC and SA looking for the packages/special items was half the damn fun of the game. In IV, it was a pain in the ass killing all the pigeons and not really satisfying either.
Ultimately, there has to be a way to combine the fun and re-playable activities of the III trilogy with the realism of IV. I understand where they were going story-wise. It just would make more well rounded and immensely replayable game if there were additional options and activities which were actually enjoyable. IV's side stuff was pretty boring and actually was more of a nuisance to have to do. Bowling for me was terrible. The only time I messed around with it was the mission where you had to take Michelle there. That's it. Same went for darts and pool. Unless I had to try and unlock a friend's hook up for Niko I didn't bother. I think they could've been put to better use if they had been incorporated into the multiplayer somehow.
It stands to reason that if they are working on the next title the game should be amazing. The amount of time has provided plenty of room to create a brilliant world and a great storyline to go with it. I just hope to hear or see something soon.