Dead? No
Less played? Yes
Summer time is over for most people. So walking around catching Pokemon in the nice summer breeze is a thing we'll have to wait for a few months. Walking in -25°C weather is not fun. School is back so less time for to play as well. Also all those sheeps that never touched a Pokemon game/played a Pokemon game in ages have also lost interest.
Am I still playing? Not like I did in summer, but I still do play. Once spring hits and the nice weather comes back, I will definitely start playing more once again.