Crimea was already a semi-autonomous area in Ukraine before Russia invaded and they were heading toward even more self government. It’s not realistic for Crimea to be an independent state. It lacks almost everything. It doesn’t even really have access to fresh water. About the only thing that it has that is valuable is it’s geography and coastline, both for military and leisure purposes. Crimea will never be an independent state in foreign policy regardless of it belonging to Russia or Ukraine but it will have more independence as part of Ukraine than it will with Russia. The most prosperous future for Crimea is as part of a Ukraine that is part of the EU it would become a prime destination for European vacationers like it was for the Soviets and unlike the Russians the Europeans will actually have the money to invest and spend.