Andros raises some interesting points. Not convinced that a tri-partite referendum will take place but option 3 seems feasible to me. There can , in reality be no argument against it. It works perfectly well in the UK where four different ethnic groups have their own 'state' and assemblies. Also, and this is vitally important for the Greek Cypriots to understand, the Welsh, Scots and Northern Irish have political equality with the English, despite being in the 'minority'. Thus a 'United Cyprus' can replicate the United Kingdom.
I do know, for a fact, that were a further round of negotiations in Cyprus to fail, a referendum will take place in the TRNC with the following three questions:
1: Do you wish to seek international recognition of the TRNC with unfettered self-determination ?
2: Do you wish to become a part of the Republic of Turkey ?
3: Do you wish to return to the state of affairs as per the London -Zurich Accords of 1959 and join the Republic of Cyprus ?
Mark my words, the above referendum will take place in the event of any failure to come to a mutually acceptable agreement.