Yeah a 17/18" MBP would be the one thing that might cause me to trade in my M2 MBP before 2029 or so. No need for Ultra; I would rather see M3/M4/M5 chip improvements bring us larger/thinner lighter.The 15" Air weighs around 3.3lbs iirc (American here, not gonna do the kg thing sorry lol).
That's 0.6lbs heavier than the 13" -- so let's assume that the 17" would add at least another 0.5lbs.
An "Air" approaching 4lbs. doesn't seem like much of an "Air" to me at that point. I think 15" is the biggest they should go.
A 17/18" Pro would be interesting though. It would be heavy...but there may be a market, especially if it has an option for the Ultra chip.
Today I spent some time with the 15" MBA, and I prefer the MBPs a lot, despite the cost and weight penalties.