It'll be a while. As a person who's been a panelist for many years for Kumori, I can say that this time last year, by now it'd be confirmed and we'd be looking over schedule drafts in the next few weeks (as well as emails regarding panelist badges if you qualify). Considering this is ~60 days farhter into the year now, we probably won't get confirmation and denials until Aug 15th~the end of August. At the very least, if you don't hear by teh 15th of September, wait until the 20th and then send emails freaking out (is my experience) if they haven't announced anything about delays.
I don't see it taking til September this year, since giving yourself only 2 months to finalize the schedule for guests and printing books- that's not pretty.