"So while the underlying hardware will probably be Winhoze on most installs"
Don't even understand what that means. Winhoze is hardware? Maybe you meant "Windows compatible hardware"
"nothing prevents Dell from slapping a more modern visual shell on it"
I wasn't aware that MS had altered their OEM agreements in this regard. Are you able to provide any evidence of this?
"or dual-booting it into an Android"
Again, OEM agreements in the past have precluded doing this. See the BeOS antitrust trial for details. Are you sure this has changed?
"or running Android as a VM and flapping between Android and Windows as the screen flaps"
Why on earth would anyone want to do that? I can see a few use cases such as having quick and dirty access to the internet when in tablet mode but I really cant see the average Joe Sixpack being impressed by it. Monumentally confused, yes, but not impressed.