The only real tanks u see are Maokai, Poppy, Naut, Alistar...
The rest u lot see are bruisers, mages, adcs who equipped themselves with TANKY GEAR.
It is not TANK META per say.
When u start seeing Chogath, Mundo and other tanks... then yes, u can call it TANK META. Many of the tanks, as a whole, are balanced and if not, on the slightly weaker side.
edit: Also, Sunfire Cape alone has opened up a lot of diversity on Top Lane... so pls take that into consideration too.