I think so.
There is no real reason that I can think of that Apple has not offered LTE Macs that makes sense besides avoiding carrier lock-in.
"Would you like your Mac with AT&T, Verizon, or Sprint?"
Just hearing that question makes me feel queasy, as I'm sure it does to anyone involved with creating Macs. It dilutes the Mac's image and creates a confusing and frustrating buying experience. The introduction of the Apple SIM, however, could allow LTE Macs that avoid lock-in.
The Perfect Mac Might Be Incoming
I believe that Apple potentially has the perfect Mac in the oven with the rumored 12" MacBook Air with Retina display, thinner fan-less design, and a much more efficient processor. How amazing would it be to have this mythical MacBook Air come with an LTE option and an Apple SIM?
Think about it: a MacBook Air with 12 hours of battery life, Retina display, always-on super-fast LTE connection that could flip back and forth between whatever carrier you desire (if AT&T and Verizon can get their act together).
Apple would have to make sure the software side was perfect — OS X would need some great and intuitive controls for controlling what apps are able to use cellular data. It would be a terrible experience if iTunes downloaded an entire season of Breaking Bad over your limited data plan.