I doubt you could do it with the GSL; that thing was written with the intent of giving WotC tight control.
However, 4E could very likely be OGL-ified. A lot of stuff would have to be renamed, and the rules text would have to be rewritten in the new designer's own words, but you can't copyright a game mechanic, and I think most of 4E's systems would be impossible to patent due to prior art. The same method used for retro-clones could just as easily create an... ante-clone?
I wouldn't be surprised if there's enough "open gaming" content and other OGL'd stuff floating around, such that it would be relatively easy to clone 4E. (The real work would be in putting it all together).
I suspect by the time an "ante-clone" of 4E is produced, WotC may very well be in the middle of 5E (or 6E). At that point I wouldn't be surprised if they end up turning a blind eye towards a 4E clone, similar to what they have done so far for retro clones of prior TSR editions of D&D/AD&D. (That is, assuming the regime at WotC doesn't become hardline on this issue).
Last edited: