As @Thom_McGrath correctly stated, it will happen incrementally. We will give you a list of the classes and such that you can reliably call with a preemptive thread. The performance is quite good depending on what you are doing and what platform you are doing it on.
Why are we doing this now? Well, it’s not exactly now. William started looking into this over a year ago. Way in the past we knew there was so much that was not thread-safe that it wasn’t worth bothering with. We actually had a large company ask us how much they’d have to pay us to make the entire console framework thread-safe and after some investigation, it just didn’t seem practical. However, things change as time goes on. We continuously upgrade our code and William thought that perhaps it was now more practical. It’s looking quite good. [edit] We continue to test it internally and get it ready for a future release.