I actually didn't even though about that lol It sounds good but I won't have high hopes for a potential G4+SCE mix. Dunno, I think there would have been an announcement earlier...
Adding popular members to an unit hardly make difference in sales. Buono's debut single got noticed because wota
kind of saw it as Kirarin competition, and it was the theme for the first season of Shugo Chara, thus it got noticed by non-H!P fans as well. High-King who had Aichan, Reina and Maimi sold the same exact amount of copies that Edo no Temari Uta II sold in the first week lol (27,805). Despite Konno and Rika (two of the most popular H!P members EVER) being in Ongaku Gatas, no release by that unit has gotten past 15K.
tl;dr: Sorry if I kill all the fun, but don't think that popular member in a unit (in this case Risako) = a
lot more sales for said unit. Not all wota blindly buy any release as long as it has their favourite's name on it...
If G4's PV is like SCE's ones, they'll add some anime CG
if it's like Buono's ones (which I doubt), then maybe the PV will have a cute little story or non-anime-themed set.
Though the support might just be for that page in the magazine, (haven't seen a full scan of it yet) like, "SCE introduces/presents G4"