The basis behind this argument is the fact that Night Elves banished Arcane magic from their society for roughly 10,000 years. The possibility of Night Elves renewing their ties to Arcane magic "Breaks canon."
This kind of boggles my mind because if Night Elves all of a sudden start using Arcane magic again...doesn't that become part of the lore? They banned it under penalty of death for a hundred centuries due to what they caused...if they see the new threats that will arise from Deathwing's return as a means to justify taking up Arcane magic again...who should really care from an OOC perspective? At that point it becomes lore. It becomes canon.
It's not like they never used Arcane magic to begin with and all of a sudden they can use it. They are fully capable of using it, and using it well. It was a choice to stop using use it and ban it. They weren't cut off from it. They didn't forget how. They weren't magically unable. They CHOSE not to use it. Now they might CHOOSE to use it again.
Am I in the ballpark here?