You're asking two very different questions, IMO – one being who deserves to be the next TNA World Heavyweight Champion, which hinges on an number of aspects that may not necessarily apply themselves viably to anything going on in the story that is TNA right now, and two being who I think will be the next TNA World Heavyweight Champion, which hinges much more so on a number of aspects that do apply themselves viably to the story that is TNA.
So, to answer these questions separately, as I feel is the only fair way to do so..
Kurt Angle or as much as it pains me to say it, Abyss, will be the next TNA World Heavyweight Champion, as those two are the closest in story to logically winning it at any given point between now and the next few months.
Pope, Mr. Anderson and Jeff Hardy all deserve to win the title, as all have been busting their ass to redefine their characters a bit since joining TNA. Pope is as up and coming as up and coming gets, Anderson is over like a mother fucker, and Jeff Hardy is Jeff Hardy, no more words (all pun intended) needed.