I sincerely doubt it. One, because although CR's world Exandria has some unique flavor elements, it's really not that different from a typical Medieval D&D world (Greyhawk, FR), so setting an anthology there doesn't make much sense compared to an official D&D world.
Second, I see no reason why Deborah Ann Woll or DMsGuild authors would be interested in writing for Exandria. Your whole theory that it is in that world seems centered around one of the authors being Marisha Ray, which i find implausible.
Exandria is official a D&D world since being mentioned in BG: DiA and the WotC D&D survey included Exandria as a D&D setting.
But anyways it just occurred to me we may both be right. Would you concider Tales of the Yawning Portal an Adventure Anthology?
I ask because TotYP included Against the giants update, which is about the size of Desert of Desolation, both made up 3 previous modules. So instead of being more like Saltmarsh, maybe this book will be more like TotYP, mixed in with other unrelated adventures. This could be TotYP 2, although perhaps not called that.