A friend of mine pointed that at the end of the trailer, it appears that Cayde is being carried by the Eco Stranger. It may be a bit of a stretch, considering we can't see their face, but the cloak looks pretty similar to the one the Exo Stranger is wearing on the grimoire card from D1.
Exo Stranger carrying Cayde (???):
https://imgur.com/a/ghocYi9
Exo Stranger Grimoire Card:
https://imgur.com/a/WCBtdyN
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Finding a reality that he lives in.....Portal looking area they are walking towards. He likely had some serious connections at Braytech also. May have been the one who fired back up Rasputin.