Will be a new-ish build for me likely reusing X370 but X570 will obviously have native 7nm support and PCIe 4; possible faster DIMM speed support. Depending on how good the boards are I may consider upgrading but I'd rather not have to buy more DDR4 at the moment, though price has trickled down a bit over the last month or so.
As far as announcements go, something is likely to occur relatively soon. There's a LOT of speculation and unofficial 'leaked' content floating around.