September is very likely to me, but October doesn't sound impossible either. It honestly depends how much work he actually needed to do before the character is ready. That comes first. The only way there would be a massive wait between the reveal and the release is if we're talking another guessing game, and at that point, they would've did that kind of reveal already.
They no longer are doing reveals(guessing games aside) unless the character is actually close to ready. Why would that change? If they need to take longer, they'll take longer. Could that mean till October? Sure.
That said, I do think a September Direct would do the reveal if it's close enough to be finished to do so. It's not impossible we get one separate final Smash direct either, but they don't need to do that with one character either. The normal presentation would happen later anyway, so by September's end, we should have the character(or at least the reveal, presentation, and release would be around a month together time-wise).
Or it could be by October's End. Sorry, I kind of make it sound like only September was possible with my last statement. Which goes against the point I was making. Worth saying I don't think "till December" is realistic. I could see that as maybe a mode update/actual big thing that isn't a Character reveal, though. Or it could just be "we're ending support beyond balance patches" too.
