I doubt Nash will even sign with the WWE on full-time basis. Let's face it, Nash doesn't have what he had in the 90's. He is getting on now and his in-ring work leaves a lot to be desired. When I watched him return at the Royal Rumble, he looked still and cumbersome at points. Whether or not it was because of the hectic nature of that match and he couldn't keep up with the pace or not, leaves a very pertinent point in my mind. I personally don't think that Nash has what it takes to go in the WWE any more. Don't get me wrong though, I loved seeing him at the Rumble, When Diesel appeared and started to put on that glove, I marked buckets. However, I don't think he has the athleticism or the charisma to make it work for himself any more.
My thought process is this, why give Nash a spot somewhere up the card, when there are more deserving people that could do much more with the run. If you are going to give Nash some time on the mic and in the ring, why not give it to someone like Kofi Kingston? The WWE needs to be looking to the future and not at the past. It is dangerous to dwell on the past for too long and when you look at TNA, you can see the evidence of that. Sure, having him come out at the Rumble was a nice moment but I don't think he should get any more involved than that.
That being said, if the WWE are going to bring him back for one last run up to Mania, it would make sense for them to have him feud with The Big Show. You could see that they both had some history at the Rumble and the WWE would be wise to capitalize on that gravy-train. They could package it as two big guys having a battle for dominance, or they could just state that there is history between the two. Either way, I think that is the most logical step. Of course, some of us know about the verbal sparring between Nash and Barrett, that could easily lead to something at Mania. Who knows.