This is a really interesting quote, and I'm sure that the thread could spend months arguing over it. To me it can be read in two ways: religiously or literally.
Taken religiously it implies that the Ulthuani dragons believe in either an afterlife, that the world will die and be reborn, or perhaps metaphorically that the Polar Gates are not static and will one day alter the magical landscape of Mallus. Thus, binding to the Winds either prevents the Wind Dragons from gaining the afterlife, or literally dying with the world without it being reborn, or as it metaphorically dies.
It can also be taken literally, which is if anything even more interesting. This could mean that sufficiently ancient dragons can fly between worlds, as living starships, rather than living and dying bound to a single world. If a dragon binds themselves to the winds, they gain power and alertness in the short term (in a draconic timescale), but sacrifice their identity and the next part of their life cycle. Notably, the eldest dragons can sleep for many mortal lifetimes without eating, which would be very useful for extended voyages through the void. Indeed, in Age of Sigmar Sigmar is directed to the Nine Realms by a giant dragon that lives in space.
Either way, this seems to imply that the Dragons bound themselves to the Elves to ensure their survival while they sleep, allowing them to live unchanged through a changing world. Notably Elves tend to mythologize their history, so it's entirely possible that the myths of Draugnir meeting and dealing with the Elven gods are not literally true. Perhaps he instead met and bartered with Caledor Dragontamer, helped him or some other great elf forge a blade that turned out far too powerful, only to be slain by a Chaos corrupted Elf during the Daemonic Incursion. Unfortunately it's unlikely for us to get any sort of unbiased source on the matter, and we can't look to canon for the answer.
