Any idea when the Assassin meta will die down?

It's an ADC focused meta, currently.

This is probably why you're seeing a lot of Assassins, though.

Assassin Meta .. It's ADC meta, which is why in the LCS you see a lot of comps like: 2 tanks, 3 marksmen or 3 tanks 2 marksmen.

the only assassins i see showing their face is Zed and Ahri with the occasional Leblanc and Talon, would hardly call that the "assassin meta"

just wait for another tank meta