The court said some things that were new, and some that were reminders. Both are important. The sovereignty project is a legitimate quest. If certain tests for popular support are achieved, the rest of Canada has an obligation to negotiate on the matter of sovereignty in good faith. The provinces are an integral part of all constitutional processes, including those that could lead to Quebec sovereignty.
Any province can begin a process of constitutional change.
On the surface, these things are nothing more than common sense, at least in the context of the Canadian political tradition. However, they represent a serious blow to the main thrust of the historic federal government position, particularly as represented by Liberal governments since 1968. The great advantage of such a position for the federal Liberals has been that if one dismisses the idea out of hand, there is no need to further discuss the possible causes and cures of the underlying discontent that gives rise to the secessionist impulse. Such a discussion inevitably leads to questioning the very heart of our federal structure - questioning it is better to avoid if one believes that the distribution of political power in Canada is as good as it could possibly be, short of perhaps a bit more central power here and there. This approach is simple to understand, apparently patriotic in its motives, and has the virtue of requiring no thought about significant change.