The earliest date is June 7/8, that would be 8 weeks from today/tomorrow. We can be pretty sure that PTS won’t last less than 8 weeks, so that’s the earliest possible date.
Now we have to consider TBC: they’re making a lot of progress there and basically all of the P1 content is available now for testing. I think it’s safe to say they’re on track and pre patch in May makes a lot of sense. Add 4 weeks to that until TBC launch and we’re in June. So... 9.1 and TBC both in June? I find that very unlikely.