most likely TSMC, GF is now too far behind process node-wise ... The HP and Dell would be happy to build the servers, keeps their assembly lines busy ...Who will manufacture the MS ARM chips? And the MS ARM-based servers?
It could be somewhat awkward for people like HP and Dell having to build servers using chips MS supply (whoever actually manufactures them).
I agree that power usage is a major factor.
Even in a single-server office environment, some clever engineering could produce a server which can keep running, albeit in some special low-power mode, with very modest UPS capacity. E.g. switch off the higher power cores completely. Especially with SSD storage. At present a UPS that can keep an x86 server running through even a pretty short power outage is expensive, fairly big, heavy and often noisy.
PS I also see ARM-based PCs (of whatever sort) being the natural result of people seeing Apple machines and MS ARM-based servers. Why wouldn't people choose ARM over x86 if they have even some of the advantages we are already seeing in M1 machines?
I agree that some will want to see Arm-based PCs, but for the average user, Intel is a household brand, that now 25 year old chime of "intel inside" still humms on every PC ad that runs on TV, average user is loyal from that perspective and does not care about the performance improvement, so a transition would start but it'll be a slow one