As much as I look forward to a larger city, gotta admit it's the country roads, and full ocean floor that have my attention atm. Going off road past country style buildings, and getting out of the city to go underwater sounds like it could be a much needed break from spending too much time in the city. That's one thing I wish IV had more of. Sometimes the city felt too much like more of the same, and it would have been nice for more changes of scenery.
The 3 characters sounds great as well. At first I was mixed on it, because I didn't want to collect everything 3x. However, now, I think it'll add a lot of replay value. Not to mention 3 different voice actors can break up the monotony.
I think the next thing I want to hear about now is multiplayer. I liked free mode in IV, but it was lacking a bit. Cruising around, getting into random gun fights online was fun, but there was no goal. I mean, everyone just kinda scattered, and only came together rarely, mostly at the airport. It would be nice if the free range mode had co-op side missions, and allowed others on the server to help on both sides. Like say, you accept a bank heist, and join the criminals. It happens real time in the city. The others in the city get a notice that the heist started, and can opt to help you, or help the cops.
One thing I def want to do though, get a boat like in Jaws, and go shark hunting with others

. Given that Red Dead had mountain lions, and (I'm pretty sure) their in the area surrounding where V is in the real world, they'll probably make a return as well.