Yes, the specs of Centriq and Vulcan are probably similar enough to Skylake that there's no catching up left for them to do. At best they could advance at a similar pace to Intel/IBM.
When it comes to the desktop, Intel is driven more by business concerns than technology. Putting the southbridge on the processor doesn't have that much advantage, but AFAIK Zen can run by itself with no external southbridge to some extent.
Well, Vulcan is now kaput, Seattle seems disowned and X-Gene is up for grabs, so only Qualcomm and Cavium remain as contenders in the server SoC space. I predict they still have a solid shot but it will require a lot of uncomfortable adjustments along the way.
When it comes to the desktop, Intel is driven more by business concerns than technology. Putting the southbridge on the processor doesn't have that much advantage, but AFAIK Zen can run by itself with no external southbridge to some extent.