GoDaddy is telling its clients not to buy .TV domains because the small island country is slowly sinking; Tuvalu is the small island country that is responsible for the .TV web address. The problem is that the island nation is slowly sinking and that one day the country will be abandoned and according to ICANN so should all of the address related to that specific country code.
The .TV address is popular for the infomercial types even though it technically has nothing to do with television at all but is a mere coincidence that the abbreviations are the same. Will ICANN actually force this domain name off the internet once the country disappears, probably not, it's a high value domain ending that should remain active for decades to come.
If they do decide to remove the domain ending you can be sure that lawsuits will spring up everywhere due to some high profile companies that register the domains for infomercial related products. If not you can be sure Billy Mays and that ShamWow guy will put up a good fight too.