We looked into deploying some Telrad. It's not worth the cost considering the number of users per site. We'd never make any money. For the cost of one Telrad BTS, we can deploy a full 4 sector cluster of 450. There's a lot more back-end devices and software required to run LTE on more than a small scale as well, which adds up to a lot, A WHOLE LOT.
We tested Wimax as a replacement for 900MHz. It didn't work at all with the foliage we have. And as we all know, Wimax is basically dead now. We also tested 3.6GHz 450 at a few 900MHz customers. It also didn't work. There's no reason to believe LTE will work through a 1/2 mile of trees either. Physics is physics, GHz do not "penetrate" at all, at least at the power levels we get with unlicensed and even 3650, I don't care what fancy technology you have, or claim to have.
You also have to consider interference. LTE and interference do not go together well. I have a lot more confidence in the Canopy scheduler to get bits through some noise.
I bet Cambium could do Canopy 4x4 MIMO (maybe even beam steering?) that is backwards compatible with existing 2x2 MIMO PMP450 SMs. Maybe that's the next logical step after the PMP450i.