Although not upgrading the software of the original 2015 Phab handset anymore is something one would expect, Lenovo has decided to leave the Project Tango AR-enabled Phab2 Pro without an Android Nougat update as well.
https://www.notebookcheck.net/No-Nougat-updates-for-the-Lenovo-Phab-lineup.240998.0.html
Lenovo are the worst company I know for after sales service. I've bought a phone and a tablet and both have had just 1 update after purchase (last year). I'm never buying any more Lenovo products again.