Despite talk of betrayal, this seems to be the first American-incited war of the century that is coming to a close. The kurds living in some situation of autonomy within a sovereign Syria will be a better, and more stable, outcome than what Iraq (still with the threat of civil war hung over it) and Afghanistan are suffering through. And it is better for the kurds themselves than being used as pawns for regional wars and constantly threatened. Being alive is better than being dead, which was what they risked constantly in that war situation. It will depend on what kind of settlement they achieve within Syria, but they're still reasonably well positioned to get a good one. And it look like the turkish intervention and the american withdrawal were instrumental to bring about that outcome. We'll see, but as of now there is some hope.
@Owen Glyndwr, a state that depends entirely on military/political protection from another is not a state. Its a protectorate at most, not autonomous. If they were optimistic, it was because they were fools. They have a long history of being used and discarded to learn from, they know fully well that Turkey, Iran and Iran, not just Syria, will act however they can to prevent a kurdish state from being created anywhere. If a kurdish state is to come into being, it will have to be through the gradual winning of political autonomy in the portions held by each of these states, such that it will become too costly to reverse for each government.
Then they will be a position of trying to get independent one by one, while the other states will have a hard time acting against it. That strategy is wrecked if one of the portions asserts itself as aggressively independent before the others even get political autonomy: it immediately creates a backlash against the kurds on those other countries, who are not equipped to resist it. The kurds in Turkey have already felt it, after the aborted attempted by those in Iraq, and due to this protectorate in Syria.
If this war ends with the kurds getting an autonomous regional state within Syria,
that will be a win for them upon which they can built. Slowing and without illusions, they may eventually get their state.