I take it that game experts are not exactly great programmers. Preemptive scheduling is a simple matter of organizing your tasks and paying proper homage to a finely tuned timer and refined port/signal systems rather than static variables.
Preemptive scheduling is a matter of spending more time checking that nobody has sabotaged your data than it is about actually getting anything done. The system works when processes are seperate programs that run independently of each other, but anything that has to interact with anything else will end up spending a ton of processing time just looking over its shoulder making sure it hasn't been bumped by something else. The system is frankly not very well suited for games. It's nice having some kind of unit of assured atomicity to rely on.
Well, Pets isn't a concept they haven't already done before. If they were actually making such a thing, it'd be simply a rebuild of what they did for TS1. This would be, essentially, a second chance to get it right.