Thanks for your question.

In researching your question, there seems to be a consensus that this late blooming is a consequence of the stress that was placed on your lilacs by the blight infestation. Normally both foliage and flower buds develop in the spring after a winter-imposed stress. The thinking is that blight stress mimicked winter stress. In short, after the stress imposed by the blight, the poor lilacs were “fooled” into thinking that it was time to develop foliage and blossoms. An interesting question is what does this portend for 2025?  Currently, this is a subject of great speculation among Minnesota gardeners. Personally, I think that you can expect some foliage in spring 2025. How much and to what extent are hard to predict. I do anticipate reduced flowering in 2025. See:

https://yardandgarden.extension.iastate.edu/faq/why-my-lilac-blooming-fall-instead-spring - :~:text=This out-of-season bloom,while pumpkins are in season!

The bottom line should be that your lilacs are not dead and will continue growing into 2025.

Thanks for consulting our forum.