I think killing off 32-bit apps was at least partially motivated by the upcoming transition to ARM, and they did it when they did it to put the bad P.R. on Catalina instead of ARM. (Just like they took the iPhone headphone jack away with the iPhone 7 rather than the iPhone 10/X/whatever to keep bad press from being associated with the new iPhone.)
Connected #298: “You Bought a Monument” has a good discussion about ARM Macs, including virtualization / emulation, starting at the 40:34 mark.
Much of Stephen’s perspective was shaped by a conversation he recently had with Steve Troughton-Smith about this, and (for reasons explained in the episode) Stephen came away expecting that Boot Camp for ARM, while possible, seems very unlikely. I found it fairly convincing. Worth a listen. I don’t have a horse in this particular race, so it wouldn’t bother me if Boot Camp went away.
That’s a completely different issue, of course, than a “Rosetta for current macOS apps to run on ARM-based Macs.” I cannot imagine that Apple would even consider not offering something like that. It would be a P.R. nightmare, because every single story about ARM Macs would highlight that flaw, not to mention that customers who are already upset about losing 32-bit apps would now face having to wait for all of their apps to be re-compiled for ARM? No way.
Even if performance isn’t great and it hurts battery life, Apple wants every story about ARM Macs to include the line “And you’ll be able to run all of your existing apps!”
p.s. - not that I expect anyone at Apple is reading this, but please for the love of all that is holy do not focus on making ARM laptops thinner. Even the 16" MacBook Pro is fine. Give me 2 actual full days of real use at full screen brightness while on battery, and then you can worry about making things thinner.
Narrator: “They’re definitely going to make them thinner.”