Wait have they done this before?
Like just looking at a sales perspective. Students are going to buy whatever macbook pro that is available for the back to school sales and wont necessarily be waiting for a new keyboard or 14in macbook like us in this forum. Meanwhile, people in this forum are going to wait it out. Doing both a sale and a new product isnt really what Apple does. Not to mention it would significantly increase demand and increase shipping times.
Just playing devils advocate here; I would personally want this new 14in macbook pro as soon as possible (March, WWDC, BTS), but I could see Apple selling the current butterfly keyboard during the summer (BTS) and then unveiling the new 14in in October.
Correct me if im wrong though.