I would postulate that the paradigm shift in which mobile CPU's drive the desktop had already happened. Ice Lake went 10nm and with new architecture (Sunny Cove) before the desktop. Actually we are still waiting on the architecture and the process is on the horizon.I think we are going to see a long tail overlap with RKL and everything that comes after especially on the desktop, presuming it is the last stand for 14nm.
On the PC side, for the broad swath of normal users, RKL will simply be good enough. Since it has Xe graphics it should allow for Intel to support it for an extremely long with their driver packages going forward.
And when it comes down to it, neither Intel nor AMD has that much incentive to focus on desktop CPUs with cutting edge nodes going forward. The real money being on the server side and second to that having power efficiency for mobile. Desktop CPUs have to come in a distant 3rd. As others have well said above, the OEMS are building their desktops to handle 65W-95W CPUs. RKL allows them to just keep using the same components with regards to PSUs and the like. If the global silicon shortage continues (why won't it?) how long will we see these sold?
I am not saying there won't be ADL and follow on desktop releases chasing halo positions, I just expect that even a couple years from now Intel is still going to be selling the market a lot of RKL. Especially if it stays remotely performance per dollar competitive. Will we see a 14nm CPU that uses DDR5? Ha...
Historically most mobile parts have basically been the bests parts of the wafer with the rest going to the desktop. I don't expect this to change so there is no news here as far as AMD or Intel not "focusing on the desktop." They are focused on performance and efficiency first and foremost and have been for a long time, well since Conroe for Intel anyway. Remember Intel had a rule where they had to achieve a certain increase in IPC (or more) for an equal increase in power? Or something like that, I don't remember it exactly.
As for the global silicon shortage. I have a different take on this. A confluence of events caused it. Everybody working/schooling remotely and a flurry of new technologies everybody "had to have" being two of the primary causes (graphics cards, Zen 3, SSD's, cell phones, etc..). Couple this with manufacturing shutting down for a while and there you have the reason we are where we are now. Supply always catches up with demand. We'll see crazy sales due to over-production soon enough. Whenever there is money to be made there is a knee jerk reaction for production to go through the roof and just like there was a lag catching up with demand, there will be a lag slowing down, which will cause an imbalance in supply.