>BSide songs
That's not happening. I think we're only ever getting those by 3rd year at most. At the moment, the solo slot is filled in by Step 3s. The only reason there's a slim chance of this happening is because of CCC already sorta having an MV.

>Bday songs
Very very unlikely. It looks like they're even starting to repurpose these as new solos rivals will use since, in canon, all songs are given by GKP besides those.