And even when AMD does move their mainstream desktop processors to a new socket, there's very little reason to expect them to be trying to accommodate multi-GPU setups. SLI and Crossfire are dead, multi-GPU gaming isn't coming back for the foreseeable future, so multi-GPU is more or less a purely workstation/server feature at this point. They're not going to increase the cost of their mainstream platform for the sole purpose of cannibalizing Threadripper sales.
And even when AMD does move their mainstream desktop processors to a new socket, there's very little reason to expect them to be trying to accommodate multi-GPU setups. SLI and Crossfire are dead, multi-GPU gaming isn't coming back for the foreseeable future, so multi-GPU is more or less a purely workstation/server feature at this point. They're not going to increase the cost of their mainstream platform for the sole purpose of cannibalizing Threadripper sales.