Nope: its still a terrible time to buy. Wait 5 more years and you'll be getting a much more reasonable value for your dollar.
Seriously: Just buy what you need and no more, computers are always the opposite of future proof.
I'm sort of in the market now for a new lenovo thinkpad. Love them with the 4k screens. Durable and great software support. Just waiting for current unit to really poop the bed.
Longer we hold off the better the next model will be.
Edit: wrt p620
I had 2 for work with a5000. One of them developed some sort of power supply error and kept shutting off. Lenovo support was beyond useless, no one had the special power supply, nothing in that box was standard, was a giant liability. I eventually ordered a third one through work and sent the other one back.
Damn fast machine but I can't figure what threadripper is for other than some very special machine learning loads. I can't figure what the purpose would be for a threadripper with a crappy card like a t1000.
Ryzen 9 is great and much less power hungry, get one of them instead.