Not really. There is a notion that is unsupported that the Dalaran High Elves all joined the Alliance. We know the civilian population of Dalaran was evacuated. But it is quite the leap
to assume that every High Elf who dwelled in Dalaran was a diehard Alliance supporter. A portion of the survivors did accompany Jaina to Kalimdor and settled in Theramore. And paid the price for that.
But given that Kael'thas was the leader of the High Elven community in Dalaran, it is far more likely most of them accompanied him home to Quel'thalas following the Scourge invasion AND the destruction of Dalaran. And we know this must be true because many of them returned, as Blood Elves, under Aethas Sunreaver to Dalaran and they were acknowledged as 'the elves who taught humanity magic' by Jaina Proudmoore herself.
If we were to parse it even more, the Silver Covenant is primarily a Hunter organization. They were even recruited into the Hunter order hall. Yet Dalaran is not a city of Hunters. It is a city of Mages. It seems unusual to equate the Silver Covenant, a Hunter organization with the community of High Elves who dwelled in Dalaran for millenia and whom Jaina Proudmoore recognised as the Sunreavers.
In truth, I guarantee that the Silver Covenant members had nothing to do with Dalaran prior to Rhonin becoming Archmage. They are former Farstiders for the most part. If you think they spent the past few millenia in Dalaran city, then you are conflating them with the group that became the Sunreavers. They simply gathered in Dalaran after Veressa's husband became Archmage and she was able to provide a place for them. And the few High Elf Mages who placed Dalaran about their own homes, why wouldn't they mingle with the Silver Covenant? Why wouldn't some of them join it, even if it far and away a Hunter organization. It's a group of like-minded members of their own people. Those few High Elf Magisters are not the basis for a cultural shift, no matter how long they have spent away from Dalaran. Any more than the Sunreavers themselves, who have spent millenia in Dalaran also, would constitute an allied race candidate of their own.
And those Silver Covenant members have been apart from mainstream Blood/High Elven society for twelve years. That's all.