Dear J and Fui ni were the best solo releases yet, and Tokimeki feels as good as them (if with a different focus). Though, neither of those had great PVs, or tie-ins, and Fui ni had little promotion that I can remember. Flower was just lacking all around, if I'm honest, and it's sad that it's the best selling solo yet.
I disagree with almost everything you just said.
Dear J managed to create a massive buzz. I think it was covered in all the media. I think there were also some CM tie-ins. It was a true hit with plenty of staying power. I liked Fui Ni's artwork, but other than that it was a pretty forgettable release.
Flower is is one of the most solid singles out of the AKB48 camp, imo. The funny thing is that "Flower" itself is probably the weakest song on the single. I wonder if the Moshidora tie-in helped Flower's sales at all or if it were mostly Acchan's fanbase who bought it. probably the latter.
Now for Mayu, like we said, there is a lot which will help this single: dorama, bonus pics, mini lives, four versions, fancy PV, etc. In addition, Mayu's hardcore fans are known for crazy spending
Based on that, I'd say we're looking at at least 50K. However, there is no way this single can sell anywhere near Dear J and Flower. I think this single, and even maybe Mayu herself, don't have the same widespread fanbase and someone like Acchan and Tomochin. On the other hand, Mayu's consistent top 5 ranking in the election could indicate otherwise.
So yeah, it's anybody's guess, really. This single's sales is harder to predict than Wasamin's. If Mayu breaks 100K on her own than they might as well ditch WH all together. I'm guessing somewhere between the 50K~75K area.