those are the ridiculous new JetBlue allowances we discussed a few weeks ago.
I use my 25 inch suitcase for trips of 6 weeks. I can't imagine anyone being able to lift that into an overhead bin. Also, my 21 inch barely fits into an A320 bin, so I have no idea how JetBlue thinks that this will work.
There may be a lot of travellers who are told that their carry on bags will need to be gate checked as the bins are already full with 26 inch suitcase...