I would not be terribly surprised to see that. I think that the people who are looking for 18.1 in late October are going to be pleasantly surprised when it arrives early (either late September or early October).
We are already at beta 2. A typical .1 release has 4 (16.1) or 5 (17.1) betas. Even if we allow for 6 betas (because 18.1 is special), if we got beta 3 next week (8/27) and went weekly from there, we’d have beta 6 potentially by ..
surprise, surprise .. September 10th.
Seems awfully convenient, does it not?
Let’s assume it goes 7 betas and stays on an every other week schedule until 18.0 launches. Then it might look like this:
(Table courtesy of Apple Writing Tools)