Macross and MSG is the two anime franchise that I know is popular and have several series and movies. In case of MSG, I think the development of new series is decided by Bandai and Tomino (originally), Bandai as the main sponsor IMO wants new MSG series over the decade to push the Gunpla sales, renewing the franchise for each generation in Japan.
In case of Macross I don't really know since Bandai doesn't involved directly with it, and AFAIK has been solely the work of Kawamori alone (story concept and main mecha designer?).
I wonder if future Macross series doesn't involve Kawamori at all (like Macross II which in the end only accepted as alternate universe).
Besides, do you accept any valk design that is not Hory Froating Head original?