I said a playoff spot. Didn't say anything about contending.
Of course they should. There's no point in keeping Connor and Morrissey either. They should tear it all down now since half the team wants out. However, if they don't want to do that, they can put together some moves to still try and make the playoffs.
The problem with rebuilding, is that nothing is guaranteed. You're more likely to end up back in the mushy middle again than be an elite contender though. Law of averages. 5 elite true contenders at any given time, 5 teams that just suck, and 22 teams where a career year here and there might get you to the playoffs or a crazy run for the Cup. Just like you're more likely to never get out of the 2nd rd than win the Cup even once(see Washington). Rebuilding isn't done at the drop of a hat. The NHL is a business, and nobody wants to suck for 5 years with no guarantee you get anything for it.
Saying that, one of the best times to actually say, ok, we're going to start over, is when top players start wanting out. Buffalo, right after the lockout when they had those great teams, and both Briere and Drury walked out on the same day in 2007, they ended up wasting 6 years trying to be competitive, until they finally dealt Vanek and said we're done.
The Jets could get a ton for Connor and Morrissey, in addition to whatever they could get for the other 3, and start a real rebuild. But if they don't want to, it doesn't matter if they should.