Scirra said on the forum that if the subscription won't work they would (logically) consider other options in the future. Unless Scirra evaporates instantly into nothingness, you don't have to worry about your projects. I think they would release a purchasable offline editor, etc..
But just as Elliott wrote, the subscription model will ensure that Scirra will be in the game with continued income and support. While I understand your thinking and feelings about this topic, I don't think that we have any reason to worry about that.