I cannot edit my anser anymore so posting this right below:
I upgraded our distributed environment the other day from CME 1.6.0p22 to CME 2.0.0p3 without any problems. So I can confirm, that during the upgrade process 2.0 and 1.6 were able to communicate through livestatus and after all hosts where on 2.0 the configuration sync worked like a charm.
So to anyone reading this: Go for the update, it is totally worth it! Just follow the docs linked above thoroughly. 