Doubt they'll kill the 1900x Anytime Soon as it's a good design for heavy I/O loads due to the full 64 PCIE lanes. What I suspect is they'll do is continue offering it as it fills the hole between Ryzen 9 and Epyc. Both the 1920 and 1950 threadrippers will dissappear since the 2920 & 2950 are already available for the enthuisist market.
What folks buy the 1900x for is that I/O capabiity as File Servers and such tend to need lots of that. Even makes a solid Web Server (mid range maybe) but still quite useful. I've looked into using one for a home file server - store everything on it with minmal storage on the local machines in the range of 64GB if I can find them with decent specs.
Enough to boot Windows and provide some local storage but everything else on the network.