So I checked, and it was
47 minutes.
The Mac topic started at minute 5.
M1 chip: 18 minutes
Air: just 7 minutes (huh)
Mac mini: 5 minutes
Pro: 7 minutes
Then 5 minutes of wrap-up.
I imagine the M1X (I still hope it won't literally be a M1X, i.e. last year's technology but with more cores and maybe higher clock) won't be quite as exciting to talk about as the original M1, so fewer than 18 minutes.
But then, all three of those Macs were essentially their Intel equivalents with different internals. No redesign, no significant feature changes.
Contrast the iMac!
That event totaled 61 minutes. It introduced AirTags, a purple iPhone (which was then killed off again half a year later), and that's it. Wait, no.
The iMac segment starts 19 minutes in, and takes 19 minutes total.
The iPad Pro segment starts 38 minutes in, and takes 21 minutes (huh).
So, if the 14- and 16-inch MacBook Pro are a significant design change they won't be 5-7 minutes each like last year, but closer to 19-21 minutes in. Not each, but taken together.
Then, suppose the M1X intro is about half as long as the M1's; that's another 9 minutes. Then another 5 minutes each at the start and end for padding. Now we're at 39 minutes — which is only 8 minutes shorter than the M1 event. Which I think means we'll see one more product. Maybe AirPods? Maybe they'll pad the beginning more with additional TV+ stuff? And there's always the wildcard of showing some Monterey details; possibly even a previously unannounced feature for it.
TL;DR: I'm not sure they'll get away with just doing MBPs for Macs, but if they add AirPods, maybe.