The capacity of the complex is around 20 to 25 elephants give or take, with this accounting for bulls too. With that in mind, I do think we could expect to see the goal to be for the herd numbers to double within the next fifteen years (until 2040). This can easily be achieved via the ten calves you mention above (which accounting for the eventual passing of Mek Kapah at least), should eventually give them a herd numbering in the late teens.
The 2028 cohort is also all pretty much confirmed - all three current mothers will breed again. I'm hoping Dokkoon will also be given the chance to have a fourth calf being a valuable founder, but I do understand why she may not due to her age and current representation.