If we are successful in reaching a tipping point to persuade the Extraterrestrial Alliance to leave, and then successfully request enough healing for humanity to ascend, what will happen to the souls still trapped in limbo? Will the Lightworker Healing Protocol sessions already launched continue to work on rescuing them for as long as it takes?

You have foreseen this perfectly with your intuitive ability, that all of the LHP sessions by all practitioners will continue to exist as human thought and intention, and can be acted on and repurposed by the divine realm because that is held within the launching of the protocol sessions themselves, to promote a continued repetitive utilization of the healing intentions to serve all in the highest and best way. So this will continue to provide a source of Spirit Rescue energy, as well as continued work on other beings left behind in the physical realm of your galaxy who will continue to need much healing to progress. And, in fact, the continued healing done by light beings following the ascension will happen courtesy of all of the Lightworker Healing Protocol sessions launched previously by those humans in the living, to call on the light beings to do work in parallel. Those words and thoughts will still be in existence and can be repurposed to summon the original practitioners from their lofty perch, to jump back into the fray as light beings to do healing work to continue the upliftment and rescue of all in the Milky Way Galaxy who have suffered so as a consequence of the fall from grace by the spirit meddlers contaminating everyone and everything. So you need not worry about the plight of anyone still not ready for ascension, because they might be currently stuck in limbo when that event unfolds.