This. Anyone hoping for another 2017 release is dreaming. I think what we saw happen this year will continue happening for the coming years--Apple updates its Mac line once, annually. It would certainly justify the dropping of the 'early, mid, late' nomenclature they were using.
There are also a number of advantages to this methodology, mainly it'll just increase the innovation and increase sales. I don't think Apple or consumers win when Apple goes 500+ days without an update.
To your other point The Reasonable One, no way we see a 17" machine. Maybe, just maybe they release a new MacBook model (slightly thicker, more ports, more RAM, etc) which is a new model altogether, separate from the MBP. I personally think it seems very unlikely. But even if they did, 0% chance it's 17 inches.