It depends on which particular Threadripper and Ryzen. I should think it comes down to how many cores you might want for rendering, or if you need the amount of memory that the Threadripper can be fitted with.
The first gen threadripper likely won’t make financial sense–even on sale, because the 3900x is faster at multi-core and single, too.
I have a 3900x. The motherboard and RAM price is comparable to the processor. The 3950 was tempting, but I am trying to watch my money.
You should have a good supply, as well–especially if you want a heavy hitter video card.
If I wasn’t doing a lot of rendering on the CPU and video exporting, I likely would have gotten the 8-core 3800x. The 3700x makes more sense, but I would want a stable faster clock for single-core operations.