While the Keynote is about iPhones, does Apple decrease prices on other products after a keynote?
Apple normally take the store offline "for updates" during a keynote (I suspect its more about making sure that there's a clean cut-off date for old products/prices across all the timezones as opposed to Apple not being clever enough to update a live website) so if they
were planning any price/spec changes to iMac/iPad the that's when they would happen.
However, there's no particular reason to think that they
are planning any such changes, since they've already had iPad and Mac annoucements this year and, presumably, they'll have an iMac Pro launch at the end of the year.
There's a pretty strong precedent of these September events being completely iPhone/Watch/Media-centric. I guess there's an outside chance that they announce the release of High Sierra.
If you're planning a major Mac/iPad purchase (esp. iPad - the last Mac announcement was
very recent) right now, then it
might be worth waiting a week, if that's convenient - but its very much "just in case". I'd also point out that, especially these days, prices can go up as well as down! Also, if they do switch new Macs to High Sierra I wouldn't be first in the queue - remember that the early worm gets the bird, the second mouse gets the cheese, etc. Me, I'll probably wait until the first update...
