We're back in San Andreas (modern day) :). My first stop, that beautiful next-gen mountain.
The more and more I watch this (and more importantly listen) the more I agree this sounds like Clifton Collins Jr. who actually voiced Cesar Vialpando in San Andreas.
Please note that I don't think that's actually the character being portrayed here. But, since Collins already has worked with Rockstar it's not that farfetched to believe they might have hired him to voice a new character, which may or may not even be the main protagonist of the main storyline.
I'm hearing lots of people saying this is Ray Liotta reprising his role of the now aging Tommy Vercetti from Vice City. I admit that the graying man found throughout the trailer may indeed be Vercetti, but I guarantee the voice in the trailer is not Liotta and likely not a representation of Vercetti.