Interresting topic, few months ago i would say YES he will win another slam without hesitation, but right now not so sure. He looked far better player in 2009 - stronger, better server, much better fitness and just he looked like future No.1. I am big Delpo fan, but look reallistically here on things.
Now he is almost 2 years back since injury- he came back in late 2010 don´t remember exactly i think it was some asia tournament or indoor, but it will be 2 years and really he had all the time to come back and he is really not as good as he was. Serve and fitness are definitely worse and even his agressivness is gone, he seems to be way to back. His only luck is that after Nole and Murray out of HC slams in 3-4 years there is nobody to win them from new generation so far, also he can be succesfull at RG in future, but how the times goes he haven´t done nothing to suggest he will become better. I mean everybody here including me thought when he came back we will have now top 5, but really it is either big 3 or big 4 but no big 5 for sure. Honestly is he better than Berdych, Tsonga or Soderling was? He won slam yes, but since his comeback he is not at higher level than those guys are/were. Also his USO victory is overrated. No matter how bad Roger played o.k. he beat him, he was down whole match but won, impressive, but his SF Nadal demolishion wasn´t such impressive considering the fact he was in great form on summer HC and Rafa post-injury 2009 wasn´t as good as Rafa 2008-early09 and his level on fast HC back than wasn´t such impressive.
So look realistically now, we don´t know if Rafa will be back or what his level will be but with Nole and Murray here i have hard time to see him winning HC slams in next 2 years at least, unlees he improove visibly, also i would favour Nole over him at RG+ with his limited fitness RG can be problem.
Imagine Berdych winning this USO-don´t think so, but imagine Berdych ending up 2012 USO champion- he would be immediately greater player, just like him 1 slam + slam F, another slam SF and MAsters 1000 title... besides his USO he haven´t done so much, since his cameback he wasn´t even in slam SF.