Those who were dispossessed had a very wide range of fates. Some of them decided they could no longer stay in Ireland, some of them left. They went in vain - they went to continental Europe. Some of the more famous figures (Owen Roe O’Neill, for example) comes back in the 1640s to fight during the Irish wars of the 1640s. So some clEarly go to serve in armies abroad; others stay at home and basically become bandits in the countryside - the English refer to them as ‘wood kerne’. These are people who are perceived as a tremendous threat to the Plantation.
But it would be wrong to over-stress the number of people who were dispossessed because the population of Ulster in the late 16th century was the lowest of any part of Ireland. So there were enormous areas where there simply weren’t any people and it’s these areas which are colonised very heavily by the new settlers. Equally well there are areas that are simply left alone, which are never colonised - the areas for example around Ardboe, around the Lough Neagh shore, which has remained almost a sort of enclave almost up to the present day. Again the southern part of the Ards (again a very different sort of world) was the Savage estate, not colonised at all by settlers.
So the experience of dispossession is very variable: in some places it’s quite extensive and the response of many of these people is either to flee into the woodlands or to go abroad; in other places there is almost no dispossession at all.