barring some extreme change in turkish policy, the precondition for an independent kurdish state is for turkey to leave nato. so long as turkey is in nato, this cannot happen. but, here's the thing: this is less unlikely today than it ever has been, and not at all outside the boundaries of possibility.

however, there is essentially no situation where a turkish invasion is avoidable. it's stated that the turkish kurds might get ideas. rather, the more likely outcome is that the north of iraq becomes a turkish province.

the key arbiter here is of course the americans, and there are several reasons why they do not want kurdish independence. to begin with, it keeps the kurds as an ally. blowback is likely at some point, but so long as it works these perpetual promises are likely to continue, with no end point. second, it gives the west indirect control in iraq. third, it continues the kind of instability that the americans desire to maintain divisions in the region. this constant "kurdish problem" in turkey is actually useful for american policy, in restricting their ambitions to the south and maintaining a buffer zone between the turks and the saudis. the americans do not want a hot war there - it's why they're bombing isis.

it's almost impossible. they'd need the turkish-american alliance to collapse, and then need to win a war against turkey. it would be a kink in american foreign policy for them to have to pick a side (and they'd probably fund both with the intent to create stalemate, requiring one (likely the kurds) to seek outside help), enough that the kurds will continue to be successively talked out of it.