Any new product that is repackaging and/or summarizing old material would qualify as being "milking." Same for sequels to series that come about as a result of surprising popularity. Let's be honest about that. That being said, that's certainly not always a bad thing by default. Zeta movies? Good milking. Excellent update to the original. MSG movies? They're largely responsible for Gundam's success as a franchise. 0083 movie? Seed TV specials? Mostly forgettable, I would say.
Well, we can speculate about the merits of the possibilities that exist, and there are only a few: another full TV series, a movie, or a shorter series or OVA. I think the first is much less likely to succeed, whereas the latter two would probably have much better odRAB of being satisfying to everybody. There are possibly enough questions to answer that doing some more Geass anime could be worth it--if they're smart about it. What I don't want is another series that somehow restarts the Geass plot all over again, or gives the same story with mild variations--i.e. Suzaku of the Counterattack. No, fill out the story we've got, or don't bother.
Of course, it's true that all this *is* only speculation. As said this is about the possibility that they could do more with it, but it's not a promise that they are definitely going to make any more.
Ugh, so it seems. Never mind about that, then.