At the end of the day the Ukraine is a neighbour and whether they want to play nice or not is actually important.
A friendly Ukraine is good for both Russia and the Ukraine.
Obviously external powers might like to see conflict or at least friction there like the US or UK, and both sides need to be aware of that and not give in to the easy temptation of conflict.
Sevastopol has a long history in the Russian navy and it is not something they could easily turn their backs on, but you have to be realistic... it is in a foreign country now, which is never the best place to base an entire fleet HQ.
Russia needs to treat it like any other foreign base... use it and maintain it but don't count on it.
The worst case scenario would be demanding a referendum, but lets face it... referendums are only held when the people in power are sure they will get their way.
Look at the EU referendums in Ireland etc... they kept having them till the result was what they wanted and then they stopped.
A referendum would be a way for the Crimea to declare independence, but equally it could be a way for the Ukraine to kick the Russian Navy out if they manipulate the results.
Do you think the west... or should I say the "international' community would respond to dirty tricks in such a democratic process if the goal got the Russian Navy out of the Crimea?
I think the solution for the foreseeable future will be to be nice to the Ukraine and maintain friendly relations.