From what I gather, Warner Brother released this album without Prince having any say in the matter - in that case, does anyone know would Warner Brothers be able to release another type of album with unreleased material?

Smillan said:

Prince is no longer contractually obliged to deliver further new material to WB for release, and WB has no contractual right to release further unreleased Prince material.

Smillan said:

The answer is 'No'.
Warner Bros DIDN'T release 'The Vault...Old Friends 4 Sale' without Prince
having any say in the matter at all, it was the other way round...
Prince issued them with the album as a 'take it or leave it' contract filler.
The only decision WB could make with the album was whether to release it
or not, and if so when.

langebleu said:

That being said..Does warner brothers still have unreleased material that they cant release?

mplsmike said:

It's a possibility.

I sure he doesnt want his past [vault] stuff to over shadow his new stuff.
But if he were smart ,he make a deal with WB..to put stuff out..
Im sure they work with him again

mplsmike said:

Only in the form of in-house promos etc.
Not in any format that could actually be used.