The reason it was only just upgraded from 5 to 10 was because you have to take database stuff and storage into account. Doubling the limit for all players to have access to is quite substantial, let alone octupling that limit. If they keep increasing that stuff I imagine it would be slow and gradual than a big chunk at a time, to see how things hold up and cope.
Yeah they've said multiple times you'll be able to share songs. Pablo has also shown chat/hud things in the works of being able to link your created songs in chat on his Twitter.