They're going to update every November, like the iphone A chips. The ones released in January were for November 2022 but were delayed because of factory strikes in China.
Just buy what you need when you need it. There will always be something new around the corner. Heck, if you think about it, the M4 laptops are probably already being considered and developed. When they come out the M5’s will be the same position and so on. It’s just how it is.
I think if you're wanting a big power CPU year, this is it if you can pony up for the M3 Max.
If you want a big GPU year, I think next year may be it. Although I think we haven't seen all of the benefits of RT yet.
I don't see the M4, also being on 3nm+, being much faster. I don't think there is a lot of thermal headroom for it, except maybe on the lower and mid tier CPUs. But I feel like they didn't do a ton with the raw GPU performance this year, so they will optimize it a lot more next year and beef it up.
TSMC at various times have claimed they have improved processes coming in the near future, and even though the next round of Apple processors will still use the misnomered 3nm, there could be small bumps in throughput.
Apple does not sell chips. Apple sells computers.
I suspect the next round of computers will see efforts put into displays, interfaces (e.g. TB5), and so on. Expect minor processing speed improvements.
As others said, I think the plan is every 12 months in "November". Also as other's said I don't thing the M4 is going to be a huge upgrade. With that I'm personally hoping Apple then decides to bump up standard RAM/Storage configurations finally to juice up demand.