I get all the enthusiasm for Alena right now, but in the longer term beyond this season, I still put my money on Sasha and Anna.
Why? Body type. Whereas Anna and Sasha are svelte (or, in Sasha's case, athletic and toned), Alena is boxy. Tiny, yes, but boxy.
That's not an issue now, but as her hips begin to widen, there's a good chance of her becoming bottom heavy; the closest analogy for this might be Samodurova's body development over the past year, and we're all seeing how this has impacted Sofia's skating and jumps. Actually, now that I think about it, Lipnitskaya's body development might serve as an even better analogy for Kostornaia.
I get that this might not be a popular opinion - and it's far from a sure thing, as body development can be unpredictable - but, again, if I were betting long-term on any of them at this point in time, say for Beijing 2022, I'd be putting my money down on Sasha and Anna over Alena for this very reason.