I doubt they will be reusing voice actors from the trilogy. It's entirely possible, but I don't see it happening.
They literally used Zevran's VA to voice the DAI protagonist, so >.< Worst decision ever if you ask me. Oh and also Fenris voiced Samson (major antagonist) and the dwarf guy you give the mosaic pieces to. (So my two previous LIs... thanks, DA team lol ugh).
Well I'll probably play the male protagonist first and most often, so I'm hoping for something not too stereotypically macho/manly/soldier dude, especially if this not a soldier character (I'm hoping for an explorer/outlaw type, but who knows). VAs I've liked so far are male Hawke, British male inquisitor, and American female inquisitor. I didn't like either ME voice; for Mark Meer, he is talented, of course, but I just didn't like the way they purposefully directed him to not emote and sound so flat. I want to play a character who actually has personality.
Garrus's VA actually wouldn't be bad; without the voice altering tech on his voice, he wouldn't recognizable as Garrus, and I think he has a nice voice.