What if the tank update shifted some tanks to excel in other lanes?
Mid lane in particular, which is pretty much only for AP carries and assassins. Currently, we only see tanks in top and jungle. Or, if they're unlucky and stop being good at either, they turn as supports 
I think it would be very interesting to see at least one tank being encouraged to head mid. This is one of the very few things I think the marksman update got right; we see some marksmen shifting into other lanes and becoming meta there. Corki mid, Graves in the jungle, Quinn top (existed before the update, I know, but never really gained any popularity until she was reworked.)
Riot should continue this trend with tanks and allowing them to compete with other lanes and against the entire roster. Possibly even letting them go bot with a support, while a carry heads to solo lanes.