I love having Cena back on the show as he makes the WHC feel at least somewhat relevant again but he really should have taken more time off IMO. WWE doesn't need Cena at the moment and the proof is that ratings haven't really taken a hit in his absence (well, they kinda have, but there is a direct correlation between it being because of Monday Night Football and not a lack of Cena) and they haven't improved at all really since he's been back. In fact, his promo and six man tag team match the night after HIAC even lost viewers (Bryan and Punk got the biggest rated segment that night, funnily enough.)
With Wrestlemania coming up, and more precisely, the big 30th milestone Wrestlemania coming up, I'd want Cena to be as healthy as possible, not rushed back and then possibly ending up having to take more time off right when you're on the heels of building towards your biggest show ever.