There's pros and cons to preemptive and cooperative scheduling policies. I wouldn't be comfortable labelling either as weakness. It really depends on context.
I've heard rumor of someone working on a preemptive scheduler. The current cooperative one is about to have runtime backpressure added to it which is going to be a really nice scheduling win.
For the kinds of systems that are built with Erlang, which is a niche that Pony seems to want to occupy, I would argue it's inherently better to have preemptive scheduling. A cooperative scheduler will always be an open invitation for bugs relating to CPU hogging. Not having to worry about these things is priceless.
I've heard rumor of someone working on a preemptive scheduler. The current cooperative one is about to have runtime backpressure added to it which is going to be a really nice scheduling win.
https://github.com/ponylang/ponyc/pull/2264