I am fully anticipating the end is near, but we won't see it until October.
We're in Gamer Season and traditionally, we've yet to go high and dry during a Smash speculation season during June. I think at least one reveal is all but guaranteed, worst case scenario being very late June. (Closest was a fakeout where we thought June would be dry after back to back Pokemon directs last year).
The other/s... well, this is certainly going to be a hot topic. I don't believe we're getting a double reveal to close the pass here and now, and I'm going to ignore the possibility of another bonus fighter as well. I believe, that there is going to be a period of time where one character remains, and it's every man/woman/person/being for themselves.
Reveal this month: Challenger Pack #10. Release: July at the soonest, September at the latest. Probably early-mid August or the end of July.
11... I'm thinking October, but maybe September. Unless we're getting two star studded reveals (or conversely, one character is so awful/controversial that they need a huge star/fan favorite to serve as a good pill to swallow to prevent blowback, which I would doubt Nintendo would want in the first place), I don't think we're seeing a back-to-back June reveal. Release is probably December but holding out hope for November, or even late October if they're revealed in September, isn't unreasonable to me.
And with Challenger Pack #10, they will either announce a third pass really is in development, or they will finally reveal to the west that this is, indeed, the end of the road. I don't think they're going to leave that information hidden away in obscure materials only superfans would notice. I expect the latter.