Most high end AM4 Motherboards have sufficient clearance to allow a TR cooler with an adapter plate on the AM4-MB so buying one for a later upgrade might be possible.
Note: I have a TR cooler running on my AM4 board (custom loop though so not completely comparable) and there is more than sufficient space to place it.
You can't use an AM4 motherboard[1] with the 1950X - you have to use an X399-chipset/TR4 motherboard, which cost more than AM4 boards (and likely have adequate room for TR coolers)
This was as a response to the idea of using a ryzen as alternative to a 1950 and solving possible thermal issues if they would occur. I never mentioned using a TR on an AM4.
It appears you may have misunderstood the comment you were replying to upthread - the original debate was if buying a 1950X at $499 would be cheaper/better than a $750 Ryzen. @lhoff pointed out that even when the 1950X is cheaper, you'd still need to buy relatively expensive coolers and mobo (for TR), meaning you won't be saving (much) on older tech. Thermal issues weren't the subject (except as an explanation on why TR4 coolers are expensive).
In turn, I misunderstood your reply to @lhoff, because in that context, I read it as a rebuttal of the idea that TR parts being expensive by suggesting an AM4 mobo + TR4 cooler as substitutes on a 1950X system.
The X570 boards won't be cheap and are probably comparable. Quality requirements for PCIe 4 are pretty significant. Depend on your needs an older ThreadRipper might be a better move. I'm not that convinced and will probably go with a 3950X in September (unless the next generation of TR is significantly compelling to wait longer).
Threadripper 1950x comes with the same core count, more memory channels, more PCI-E lanes and more memory. You can grab one for $499 from amazon.