First of all, your participation on those timelines underway at the time of a possible annihilation that is envisioned would still play out to reach an ending of the life on those timelines, according to local conditions and any other influencing factors, including from the timeline experiencing the mass annihilation. This would be a negative karmic energy projected forward through the looping of time, so you would still be in existence on the other timelines but under less-than-ideal conditions, because you would feel a consequence of those negative energies beginning to impinge.
Regardless of their impact, when you are done in that timeline, that portion of the soul involved in the future life projection would rejoin the soul in the light but would not reincarnate on that future projection, as its existence depends on what is happening in the current life because it is a future projection of the current life; those that are essentially prior lifetimes that might be still ongoing and partially overlapping would similarly reach a conclusion for portions of your soul, and those soul extensions would return to the light but not be able to reincarnate on those timelines. When the past is over and done with, it is over and done with. The future projections continue to the extent there is a current life underway because the future extension depends on the current life for its genesis. When all incarnations in earth plane come to a halt, there can be no further human life extensions beyond the point when everything ongoing prior to and during the annihilation, in effect, phases out through attrition, such that the beings are not replaced. So these timelines become, in effect, a dead end, they are vestigial because the reason for their existence has been removed. When the Divine Human Project comes to a halt, there is no purpose for any further incarnations on other ancillary timelines as the future destiny is truncated because of the annihilation being successful to remove the launching pad, being incarnation on the Earth in the physical.
So what this represents is a significant restriction of possibilities for human experience through incarnation. Because the soul is immortal, you will go on, and those portions of the soul involved with incarnation currently, will still be in existence but within the light in the higher astral plane with fewer places to go, to contribute as a physical human and all that is planned for its glorious future through the learning gained from the service in solving the problem of evil in your galaxy. If the project fails, this will be a major setback because there will need to be a retooling and a decision made whether to restart another repopulation of the Earth, if available, or even perhaps a restart of the entire universe to work on a solution for this problem in a fresher recreation with some built-in adjustments to increase the likelihood of success. So depending on the directions things take, there could be a delay of many billions of years before you, as divine humans, could truly spread your wings and benefit from having free agency and free will as light beings. So make no mistake, there will be a penalty, a very real consequence of annihilation if it cannot be prevented, and soon, because the timeline is so short leading up to that planned event within the next five years or so.