Consider, a Turkey that enters the EU will abide by the Aquis. Which means Greek Cypriots will be provided freedom of movement to the north and the right to return to their property by virtue of the Aquis. This is why entering the EU was important for the Greek Cypriots, not because of veto threats over Turkey. So, the Greek side may agree to Annan 5 with the knowledge that the deal gets worse with every passing generation, or they may simply decide that doing nothing or even partition is actually better than the Annan Plan.
But ultimately with the acquis, a European Court will simply ask the EU member (Turkey or the TRNC) to set up a local court to decide on these property issues.
The problem right now is that the TRNC is unrecognized so claims get funneled up to the European Courts. Once the north joins the EU, it will be responsible for making these property decisions, knowing of course that they can be appealed ultimately to EU bodies.
The TRNC right now does not vouchsafe stolen properties for those who are in effect squatting on Greek Cypriot land. The land registry in the north is in chaos (for that matter so is the one in the south). Whoever buys up north cannot be assured that they will keep their land.
I am mystified that Britons can actually be convinced to buy "villas" in Northern Cyprus. We have met the enemy, and he is us — Pogo