I would still wait for a Ryzen 5000 CPU. You are so close, and the performance uplift is massive compared to Ryzen 3000/Zen2.
Stock is regularly arriving - most retailers are still filling preorders. Everything I've read coming from actual retailers suggests it's not that bad and stock is regularly arriving but not in huge numbers. Canada Computers is getting Ryzen 5000 stock every 2 days, for example, but they won't ship them
I'm in the exact same boat as you, I have an entire build ready to go but missing a 5950x. No way would I consider a 3950x at this point but I guess it depends how badly you need your new PC up and running.