Jets still would just be kicking the can down the road in this case and trade him in the 3rd year

they should trade him and schiefele now before thet lose them for free

True but atleast it keeps them somewhat competitive and they have the option of blowing it up at next years deadline with Scheifele on an expiring deal and Dubois too with 2 more years signed. Can fetch a couple 1sts and set off a rebuild then. But for now it allows them to go in to next with the intention to compete and kicks the can as you say to atleast the deadline to see where they're at. And if they're in it they'll have a good amount to re sign scheifele with the cap going up $5M the year after and Dillon's hit coming off the books.

Problem with this is you are pushing his next contract into older territory.
If he's closer to 30, that means 35 at the tail end, which most teams are trying to get away from by locking in younger players for term sooner.
A lot can also happen in those 3 years where Montreal no longer has the roster spot and/or cap space.

Nothing wrong with it for WInnipeg if they can get more years out of him, he's someone else's problem by then. It's just less likely to line up with Montreal's plans so he may have to go elsewhere.