I dare say by the time Weidman is good enough to beat Anderson (if ever) that anderson will be pretty much retired.
Well, who honestly knows at this point. Anderson looks like he could fight for quite a few more years if he actually wanted to. But Weidman is already scary good and is only going to get better and better. IMO he posses the blueprint skillset for beating Anderson, while Anderson may be the best mixed martial artist on the planet, he's not immortal.