I'd prefer not to leave the decision solely to the developer team, involving users and early adopters who have the feelings about the maturity of the product.
My opinion, based on the kind of work we did in the last weeks is that NethServer 7RC3 is mature and that it will probably be the last version before final.
But I'd like to hear voices, I may be undervaluing some aspects of the system.
Regarding time, I think that a couple of weeks could be a good time frame to try to discover more problems with the newest features of 7 (read samba 4 AD).
I personally consider RC3 as Final (with these small improvements which shouldn't block the release: https://github.com/NethServer/dev/projects/2).