In short, one possible scenario goes like this: While gamers might not be into it initially, the publishers will be (no used games = more sales), so they'll flock to the console(s) that blocks used games, while abandoning those that allow them. As a result, all the major titles will be coming out for that console, forcing the players to switch to it or not get to play the major releases.
Now, that's just one possible scenario, but it's not an unlikely one. Also, while dedicated gamers fuss and protest and boycott and whatnot (as consumers should do when faced with bullshit), the general public is willing to accept quite a bit of punishment and still fork over the cash. Since the publishers follow the money, the market segment that is actually sufficiently aware as consumers to actually care might end up being too small to be truly relevant.
Basically, if they want to block used game sales, they'll most likely get away with it. Sucks.