I have the impression that Tahm Kench will someday become pick or ban

Seriously, is a very good champion.

He can eat allies, protecting them from ganks and all-ins. He is a very good counter to a number of popular supports, namely Thresh and Blitzcrank. He has a Pantheon ult that can be used to bring an ally, too. He has a powerful hard CC (although it is extremely conditional) He is very difficult to kill, thanks to his Grey Health mechanic. Grey Health also means that Tahm Kench is difficult to poke, unlike other tank supports. He can prevent a dangerous assassin such as Zed from killing his allies, just by stacking "An Acquired Taste" on them and eating them.

If all that weren't enough, Tahm Kench can also be used as a top laner. I have yet to see a Tahm Kench top lane, but I suppose that he would be a good counter to other tanks and bruisers, due to his Grey Health and his high base damage. He would also be difficult to poke with long ranged mages that make other tanks have a hard time during the lane phase.

I am extremely sure that once Tahm Kench is used on a LCS match, he will suddenly become popular, people will realize how strong he is, and he will become pick or ban, soon.