There's a new rumor, AMD might be planning a new motherboard generation for the Ryzen Threadripper 2000 processors. The board partners would introduce X499 boards during CES 2019 next January 2019. In addition, there is also talk of a Z490.

X499 has been talked and gossiped about for a while now, it would offer a I/O hub and improvements. However, what these improvements entail, is not yet known. We could reason that PCI Express Gen 4 could be introduced with the Vega refresh in mind. Initially, it was expected that an AMD X499 chipset would launch alongside the second generation Ryzen Threadripper processors, Instead AMD updated X399 motherboards where launched. If it is true, the release would be right after an expected release of the Intel X599 platform which is expected to launch at the end of this year. It would be a new chip, not a refresh of the existing design. For X499 motherboards AMD would partner up once again with Asrock, Asus, Gigabyte and MSI. My problem here is that currently, I do not see a real need for a new Threadripper chipset as it is already very complete. 

Also, AMD would have plans for a Z490 chipset on the AM4 platform, that however is an ongoing rumor for many months now.  The Z490 would feature more PCI-E lanes compared to the X470 and to achieve that AMD would integrate a PLX or PEX chip on the motherboard. Earlier this chatter was pretty much debunked as such a solution would increase the cost of the motherboard, so really that would not make much sense if you ask me. As always, a word of advice, chatter on the web, rumors, are to be treated with caution and a bit of salt. 

AMD Ryzen Threadripper: X499 motherboards might launch Q1 2019