If they go with XT then does this mean no 6 core with Vcache?
Why would you say that? Chiplets are chiplets are chiplets, it makes no sense for AMD to just throw away any 3D cache chiplets that don't make the cut for a 12 and 16 core SKU, or "waste" golden samples that are a bit "too good" for the dual chiplet models.
Look at the chiplet allocation in the current 4 chiplet-based SKUs. Are all the chiplets the same quality? Do the 5900X and 5950X get slightly lower binned chiplets so the 5600X and 5800X get maximum performance? Or do the dual-chiplet SKUs get preferential treatment to keep their TDP down? Arguably it doesn't make a difference because there is still a binning requirement to populate those 4 SKUs, and that binning requirement doesn't go away because there's now a slice of cache slapped on top. And with yet another bump in TSMC's wafer costs and the little extra manufacturing cost to lay down the cache, I really don't see AMD throwing anything away just because a chiplet didn't cut the mustard for a 5900X.
Also consider this: AMD demonstrated a 15% uplift in games. I think the use of a 12 core model was purely because AMD had pushed the 5900X as their ultimate gaming CPU previously, so that narrative was continued. But everybody in the real world knows 12 cores is currently overkill for gaming. Even if big little works out for Alder Lake, gaming is still going to be a job for the performance cores, and Intel still only has 8 of those. Gaming perIt'll be a big dent for AMD's current performance leadership if they appear to need 12 3D cache-enhanced Zen 3 cores to contest the gaming crown against "only" 8 Golden Cove cores. If Alder Lake's synthetics prove to be real and translate to real-world usage (which Rocket Lake never did), then AMD are going to need the 3D cache performance uplift across the
entire product stack.
Ultimately nobody's said which desktop SKUs are getting the 3D cache treatment, but I don't see any reason why such treatment would be exclusive to the top SKUs. And if the only argument is "well 3D stacking must cost a fortune" (of which it won't), then I can see AMD pricing Threadripper to subsidise the desktop line given there's a fight on with Alder Lake.