Assuming the band decides to carry on without the late, great Chester, they'll mark 25 years of existence in 2021. Most bands that last that long get hit with the "classic rock" tag. Some people even consider Nirvana and Soundgarden classic rock. That said, how would you feel about the potential of LP being called classic rock in a few years?
I think the rap elements and weird stuff will keep them from being called classic rock anytime too soon. Maybe around 2030 or so will that start being thrown around. But who knows, it's remarkable how relatively mainstream they've managed to stay, same with acts like Coldplay.
When I still lived in Tampa about 2 years ago the local classic rock station was already playing Linkin Park. They also play Green Day, Nirvana, etc.
"2030" I don't know if I want to see the world at that time tbh Kind of a scary thought, somehow. But yeah I do see them being regarded as classic rock or something similar to that