Hulk Hogan's name still has a great deal of value to WWE, as evidenced by how often he's been used since his return to the company last year despite the fact that he can't actually wrestle. He was the host of WrestleMania 30 and it's a safe bet he'll be involved in some way at WrestleMania 31.
As he tells BANG Showbiz, he's still hoping he'll get to have one more match:
"I got some advice from a wise man, his name is Vince McMahon and he said, 'Never, say never.' I'm back home in the WWE, this is where I started, I'm home and to end the legacy and put the period on the end of the sentence I am training right now like I'm getting ready for the WWE Championship. You just never know when Hulk Hogan is going to tear the house down. It could be any time, it could be anywhere. I am training and getting ready for my last match, my last run or my retirement match. It's not over until the fat lady sings and I haven't put the period at the end of the sentence yet."
Hogan is a 61-year-old man who has had more surgeries in his life than any human should ever have to go through. While he may long for past glory, and while it would certainly be nice to say his final career match took place in a WWE ring, allowing him to wrestle at this point would be irresponsible at best and promotional malpractice at worst.
Still, he's going to continue pining and if WWE gets desperate enough perhaps they'll cave. For now, it appears the WrestleMania 31 card is filled out with no room for a Hogan match.
But like he said, never say never.