It doesn't really matter to me if they hire famous voice actors. What does matter, however, is the amount/quality of voice actors that they hire for the rest of the game. If hiring a famous voice actors means the rest of the VA's are horrible, I'd prefer they stayed away from them. If it doesn't, then I'm not opposed to it.
Bethesda has made a lot of money from their previous games, and judging by Zenimax's recent acquisitions, they're hardly strapped for cash. I think they could hire both competent voice actors, and a famous voice actor.