PS3 not being the newest console out there, meaning developing costs should go down. All the big companies will be developing for PS4.
That's not really going to help development costs, though. Development costs is basically money to actually physically make a game, and unless people are now getting paid less, or the quality drops significantly, I don't see development costs going down. You still have X programmers, animators, artists, CG guys, sound guys, etc. all getting paid Y amount of money, and that equals Z development cost. You need to decrease X or Y to make Z go down.
At least, that's my theory. I might be wrong, though - I'm not "in the biz."