I'm expecting singles for Zero (IIRC, it's typical length?) and sets for Nanoha. CCS was a disaster for Geneon as single disc releases, so I can't see them putting a show of comparable length and genre out in 4 episode singles
Zero no Tsukaima and Nanoha both have about the same number of episodes licensed. 25 for ZnT (13+12, pretty sure Futatsuki no Kishi is licensed) to 26 for Nanoha (13+13). Both would need only 6 typical singles, or two cour/season sets. StrikerS and Princesses no Rondo aren't licensed yet.
And even though CCS and Nanoha are different genres and shows, yes it will be hard to get Joe Schmoe at Best Buy to understand that. Of course, there's more than enough serious, action-y art they could put on the covers, and they can always drop the "Mahou Shoujo" from the title. I think Geneon was planning to do just that initially anyway.
Geneon will still be doing the work but it appears to be Funi making decisions about release format, and they ARE big on sets. So what remains to be seen, I guess, is if they can get permission to do these shows in sets from Sojitz/original license holders. I'm sure they will if they can, because they're trying to do almost everything else in singles.