So with Prince no longer with us I was wondering about the contract he signed with Warners to regain the ownership of his masters. I assume the contract would be, we will return the masters to you and you will give us X in return.

As no remastered or superdeluxe/expanded versions have yet to be released, and I am specifically talking about Purple Rain initially, will Warners be able to claim the ownership of his catalogue back as the contract wasn't fulfilled ?

We don't know what any contract says, so it is not possible to determine what claim - if any - a third party, such as Warner Bros. has on any assets.