There are a bunch of companies already in this space. id Quantique, MagiQ etc. Wikipedia has a list on the QKD page. Many protocols have already been developed and built into functioning systems. There are some challenges facing real world implementations, including the difficulty of long-range quantum communication which necessitates repeaters (except maybe in the case of space based networks). There doesn't seem to be a huge market at least without viable long range systems.
It is not too early to work on this, in fact many are already doing so and have been doing so for some time.
Lots of thought is certainly being put into this in the security space, given that the algorithms to decrypt today's encrypted data are ready to use once quantum computing becomes ready. That means that "secure encrypted data" being recorded today will be able to be decrypted in the future. I have heard this coming up more and more and thus the beginning of a demand is emerging as awareness spreads.
Just a little bit of googling led me to discover companies working in the space who have raised funding. So, working back from there you will find investors willing to invest.
I have heard some who cynically call this the next Y2K - in other words paranoia about the post-quantum doomsday will create opportunity.