First you'd need to define what a tech tree actually is ;)
Is it a separate "research tree" to e.g. unlock a new unit or a production boost? (Anno 1701 had a research building that was central to progression, for example, Age of Empires has a variety of researchable upgrades, ...)
Or is it simply the option to progress (in potentially different branches)?
Cause the latter technically already exists in Anno: You progress continually throughout the game, unlocking new production chains, services, ships, ...
What we don't have, of course, is the tech tree itself: No way to see all these upcoming unlocks before actually reaching them. That might be a neat feature though (<- personal comment; no, we don't plan it for 1800)