I don't think so.
The prelim DevKits for the Next-Gen systems don't appear to have any special firmware that would prevent it from playing any specific disc, and the suppliers memo they sent with them didn't mention anything about it.
Honestly, though, I don't see how they could block used games. They can "physically" do it, sure, but not logistically. A vast majority of Gamers buy new $60 Xbox 360/PS3 games by trading in the other ones they bought to lower the price of it. Getting rid of that venue will see sales plummet and recreate 1983 all over again.
Regardless of what Publishers/Developers want to say, they make a killing on the Rental business, especially through companies like GameFly and the like. Given the facts above and the impending implosion of the Gaming market if Used Games were blocked, I see the probability of this happening as very very low.
Of course, it could happen, anything is possible after all. They could send a new memo requiring that each game be coded to use an Activation Code similar to PC Games, but I truly don't believe that will happen.