I think it's fair to say that Apple has a history of putting a greater deal of thought into their new features than the average company, which makes it less likely that they drop a feature, but it still happens pretty frequently.
Some examples of products and features that apple killed, changed or rolled back:
- Puck style mouse
- Dashboard (still accessible but hasn't been developed in years and comes disabled on new macs)
- DVD over CD-R on early iMacs
- G4 cube (discontinued after less than a year)
- apparently the garbage can Mac Pros
- Final Cut Pro X
- iTunes Ping
- MobileMe
I don't think the Touch Bar is a terrible idea. It makes no sense though for pros and would fit far better on the 12" MacBook line, which caters more to casual users. touch interfaces are only useful because they allow you to ditch the keyboard and trackpad. Otherwise, they're just slow and imprecise. Any interface that helps productivity on the touch bar would help even more if it was on the screen, accessible with the quicker and more precise pointer and not obscured by the user's knuckles.
But as a marketing tool to make those who love the simplicity of their iPads and iPhones feel more at home right away or for people who are just never gonna learn keyboard shortcuts or the details of a richer desktop UI, it's probably helpful.
Personally, i would pay extra to NOT have the touch bar just because any time I try to use it, it just slows me down. But know I'm not the typical user.