Generally yes. I don't really find much pleasure in it myself. I don't think Civ has ever really been about those sort of rivalries the way AoE and other games are. And, I think even if they were considering it, the idea would fall further down the list than civs which could plausibly connect to each other across eras.
And as for evolutions, if SEA is treated the same way as Mesoamerica, South America, West Africa, SS Africa, and Austronesia, I would sooner predict the devs will just settle for ??? (Mon? Champa? Srivijaya?) -> Khmer + Burma/Pagan + Vietnam/Dai Viet -> Siam and be done with the whole region. Maybe Vietnam as a modern civ instead of an exploration civ. I just would be very surprised if the devs put more effort into the granularity of SEA (or most regions) than that.
Put another way, not only do I think that the base game is going to try to cram in a lot of returning civs to try to reach parity with VI sooner, but I also suspect new civs are being targeted based primarily on what appeared on a lot of player wishlists. That is likely why we have Chola and the Mughals. That is likely why we have the Mississippians and Mexico. It might even explain Amina and Himiko to some extent. So I do expect a lot of new additions to reflect older discourse before the implementation of separate eras: i.e. players wanted "Burma" generally, and weren't really concerning themselves with Pyu vs. Pagan vs. Toungoo or whatever. I will be surprised if we see things like Sukothai/Ayutthaya when Siam is perhaps the best modern option to for that region.