If we prevent human annihilation within the nine-year window left to us, how long thereafter will it take for humanity to be ready for the full Ascension to a higher dimension?

This again, will depend on the speed of things for humans to accomplish achieving readiness on an energetic level and a karmic level both. There will be much cleanup and much additional healing required to clear the decks, so to speak. Having the interlopers absent will make it possible, but then the healing must be carried out. So while the energies can change dramatically with a return to gentleness, cooperation among individuals, and an openness to many changes in many institutions for the better, and a commitment in helping one another to a greater degree than ever before, all of which will help progress and add to the speed of recovery from the many dark centuries humans have endured, there will still be much required to work through the prior pains and liabilities generated by human action, wittingly or unwittingly. So this will take multiple generations to reach a sufficient state of readiness for humanity as a whole to ascend. We understand this is not what you wish to hear, but keep in mind the promises of Ascension in the offing were false promises. This was all propaganda designed to create a wonderful future that was imminent. There will still be a wonderful future, but it will take some time yet to achieve sufficient preparation and have things in place needed to bring more people up to the same general level. This will be a quite useful investment in effort and time because the fate of humanity will be certain, and so the investment itself will be certain to pay many, many, dividends. This is a problem worth having, compared to facing a potential restart of the project entirely from scratch and facing the same long, slow, painful, learning curve.