Honestly this would have been such neat foreshadowing, if MtG was capable of foreshadowing something like that. Provided we don't learn about Ashiok's origins within the next three years or so, that is. They made Kaya and Dovin for War of the Spark but they appeared three years before that. So that's roughly how long they can plan things in advance due to the production cycle.
Granted, with the new-world-each-set paradigm we will burn through storylines much quicker, but I'm not holding my hopes up given their track record.
Plus, as people have said, it'd be weird if Ashiok was from Dominaria, due to how they reacted to the knowledge of Phyrexia from Elspeth. (Unless Ashiok has lost memories like Jace, which might make some thematic sense given Ashiok's powers and magic, but would also feel like using the same trick twice and doesn't truly jive with what we know about them so far.)