Isn't it better to push new talent, to continue to search for the next big thing, rather than wait until guys retire and you have no one in place to step in.
HBK just retired. Taker cannot be too far behind. Triple H, Chris Jericho, Edge, Rey Mysterio, Kane, these are all guys who are closer to the end of their careers than they are to the beginning. The WWE has to fill their shoes when they eventually do leave, so they won't be stuck holding the bag. They have lots of guys to step into the big guys' shoes (Punk, Miz, Cena, Sheamus,etc.,), but then in turn people need to fill their shoes too.
If you don't plan for the future in this manner, what are you left with? EV2.0. The Band. The Red Wolfpac. Hogan. Flair. Sting. And an uphill battle.