I also think that the timeline will be similar to Beijing. Beijing does have lots of clone ride systems (although not all are clones), but lots of the themed areas are new (JW, Minions, KFP, Transformers) so it could be somewhat comparable to EU.I think we should be looking at Beijing for a modern example of this. They went vertical last year (or two years ago, for those reading this in 2020), and they're opening in Summer 2021. That would put a groundbreaking at late next year (or this year?) for Epic Universe.
The big question is, could we start even earlier than Beijing? That park is mostly clones after all. This park is almost entirely new.
I expect that construction on the major infrastructure projects (Kirkman, BoH) will begin in the first half of 2020, followed by construction on the park beginning in the second half of 2020. If the park is not vertical by the end of 2020, then I would no longer expect it to open by summer 2023.