Won't happen on the
Mavic 2, in my opinion, for the following reasons:
1. Doesn't fit on the gimbal without significant redesign
2. (main one) would take 90% of sales away from M210/XT2 combos
3. DJI so far have not designed their own thermal camera, they have only modified FLIR OEM designs. Boson would need a ground-up solution
4. They couldn't use MSX enhancement with a Boson. MSX is a FLIR patented technology. They get around it on the Dual because the camera is a variant of the Flir One
It will happen eventually, around the same time that the M210 is due for replacement (probably in the next year or two). Smaller drones are the way forward, but given the massive price tag of the M210 DJI can't afford to lose sales of it to a Boson based Mavic.
It would also be more expensive, yes, since a low end Boson is around $1300 vs $300 for a Lepton.