In a way, it's comparable to how Michael Jordan retired from basketball to play baseball for a while before coming back to basketball.
No, I'm not saying LD in soccer is anywhere near what MJ was to basketball - it's more that when MJ came back to play basketball, he could still do so at the NBA level. Sure, he wasn't MJ of old, but that's a really high standard.
Similarly, LD wouldn't be young LD if he decided to return,
but he'd probably still be fine in league or even national team action. At least, that's what I took away from Stuart Holden's video prediction here of LD's return. It's not so much that I agree with Stu (I don't think LD will return), but I agree with Stu's implication that Donovan could come back and play at a high level.
At least, within the confines of a given time limit, like 2015. Certain things LD is good at, like his ability to keep the ball and his vision on the field, don't deteriorate as easily as stamina and other physical elements.