Realistically, owning the TM to Maradonia will mean fuck-all. Gunter and the MDO Trust have already established the use of "Maradonia" in commerce (as half-assed as it may be) so, with or without a valid TM registration, they still have a de facto right to continue using the term in the markets they have established. Since you can buy Kindle versions of the Maradonia books (and I am assuming that the money goes to Gunter), you could make an argument that the Maradonia books have been offered for sale nationally, or maybe even internationally.
I'm also not entirely convinced that the Teschs have abandoned the TM, since they are still trying to sell/market the books (again, regardless of how half-assed the attempt may be). The US PTO doesn't make decisions re: abandonment so, (in order to get a decision on that, and assuming the Teschs had a valid registration) the Tesches would need to sue someone over TM infringement, the defendant would need to use a defense of abandonment, and then a court would need to make the determination. Since the TM has been cancelled, that whole discussion is pretty much moot -- the Tesches' establishment of use in commerce without a valid registration gives them a shield, but not a sword.
Further, a TM is nothing more than a right to use a name or brand in connection with a product (and the Tesches only registered a TM for books). It has nothing to do with copyrights or derivative works, so owning the Maradonia TM would not automatically confer a right to write books in the world of Maradonia that Glo-Glo has developed.
So, what good would it do to own the Maradonia TM? Even though I believe in following the Prime Directive for lolcows, I think it would totally yank Gunter's and Glo-Glo's chains to know that someone else owns the TM for their prized IP. As other folks have pointed out, it only costs a couple of hundred bucks to register it, and all we would need to do to establish use in commerce is crank out a "Sonichu in Maradonia" comic, run to Kinko's, print out 10 or 20 copies, and offer it for sale on the Farms.
We wouldn't be able to sue the Tesches, but the owner of the TM could always make an attempt to force them to license the name, or even try to sell it back to them. Hell, I'd donate 25 bucks to the cause, and would even volunteer my time to do the TM app (it's far from rocket science).