Apple haven't held a October event for a few years now, so unless they are going back to doing that i don't know. It seemed like they had changed it around, because for the last couple of years there has been a March event, June and then September, which is then the last event Apple holds.
Maybe you are right tho, maybe they will update the iMac with minor refresh, maybe even the iPad Pro 12.9" adding true tone and a couple of other features. If they think it's worth it maybe they will hold an October event, with it being the first time they have held 4 events in one year (that i can remember).
Yeah, actually, if Apple announces an October event, we can be sure it'll be full of great and major updates (they wouldn't hold a 4th. event just to announce minor updates). If they don't, it doesn't necessary means there won't be any updates, but most of them will be minor (thus, silent).
We'll see what happens in 8 days. If they announce the big updates to the MBP, I'd be almost sure there won't be an October event (but there might be a lot of silent updates, though).