In the current LLM cybersecurity climate, I honestly can't say with 100% certainty anymore that something like a VM acts as a completely infallible sandbox environment for the next couple decades.
I think this is one of those situations where you don't need to outrun the tiger, you just need to be better at security than 99% of people, which is definitely the case if you're partitioning your life into VMs.
I wonder if/when mainstream OSes will start doing this.
VMs are demonstrably not infallible, but that's not quite the issue here.
If you only ever run your banking app inside a VM with an encrypted disk volume, and don't browse sketchy sites or do anything else in there, then you're very well protected against even LLM-assisted attacks.
One caveat in that case is I wouldn't keep the password to the VM disk in a password manager, since that then becomes an attack vector.
A keylogger would still be a viable attack vector, though. The security of operating systems is going to need to be improved to guard against some of these things, e.g. a protected input mechanism for passwords that can't be intercepted.