You know that HVS considers the sales from the first game quite well? They were a small indie dev doing a new IP for a console that doesn't have much of a market for that type of game. Were you expecting millions? They weren't.
"There are two things that are infinite; The Universe and the stupidity of human beings. I'm not sure about the first." -Albert Einstein
No, not millions and that's great HVS was satisfied, but SEGA, you know the ones who have final say on everything?
Yeah, them, they aren't going to keep funding a franchise that hasn't sold all that well across 2 games and got blown out of the water by Call of Duty and GoldenEye in terms of sales. (this is speculative, as none of the 3 games have been released)
I'm almost certain of a cliffhanger (with a little more closure than the frist game) and Conduit 3. Sure it depends on sales, but I'm pretty sure that this is going to be a genuinely good game, and in turn, good word of mouth.
Believe it or not, word of mouth is the best motor for sales aside from expensive add campaigns. I don't think this game will have much problem finding a good following to keep the series afloat.
Uncharted 2 Machinima Voice Actor. Currently playing Sully and Lazarevic. Add me on PSN if you want to get involved: Geo_Chronic.