Seems this topic has been coming up a lot recently.

Every case must be looked at differently, so in some instances it may be correct to be against some so-called national liberation projects. But to say national liberation movements should never be supported, or that these people should just "wait for the revolution" is extremely paternalistic. To again quote Marx/Engels' position on the question of Polish independence:

It is historically impossible for a great people even to discuss internal problems of any kind seriously, as long as it lacks national independence.

...

So long as Poland is partitioned and subjugated, therefore, neither a strong socialist party can develop in the country itself, nor can there arise real international intercourse between the proletarian parties in Germany, etc, with other than émigré Poles. Every Polish peasant or worker who wakes up from the general gloom and participates in the common interest, encounters first the fact of national subjugation. This fact is in his way everywhere as the first barrier. To remove it is the basic condition of every healthy and free development. Polish socialists who do not place the liberation of their country at the head of their programme, appear to me as would German socialists who do not demand first and foremost repeal of the socialist law, freedom of the press, association and assembly. In order to be able to fight one needs first a soil to stand on, air, light and space. Otherwise all is idle chatter.

It is unimportant whether a reconstitution of Poland is possible before the next revolution. We have in no case the task to deter the Poles from their efforts to fight for the vital conditions of their future development, or to persuade them that national independence is a very secondary matter from the international point of view. On the contrary, independence is the basis of any common international action.