It's far from a secret that in the Evangelion fandom, many people wanted to create a child of Shinji and Asuka, and in most cases these are girls. From Axel Terizaki and "The Child of Love", to Jimmy Volk and " The 2nd Try". But this is Western Fandom, but what about Eastern, I mean Japanese? Local members of the LAS subfandom have already created a character that more closely resembles Schrödinger's Cat. She exists because she was "canonized" by the fandom, but she doesn't exist either, because she never appeared outside fan works, and has no canon image. And the Japanese called this Metaphysical Essence: Mirai Ikari. Why so, since the word "mirai" is translated as "future".

I don't know if we can ever say there is such a thing as "established fanon", however I do recall that pre-2.0 fics almost always refered to Toji's then un-named little sister as Sakura, so, eh. Maybe this influenced Anno, since it wouldn't be the first time he'd incorporate fan reception to at least some degree. I can't find the source again, but it was pretty well known how they read on doujins for Gunbuster and Nadia to evaluate reception, and notably Ep 22 DC took direct inspiration from a doujin: thread/17938/Nobi-Nobita-Bridal-Veil-Ep-22-DC-Source/

As for this Mirai thing itself, I did a quick search and one notable artist mentioned this:

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— twitter-user (@username) date

Far be it from me to tell anyone what kinda FFs they can write, but just once I'd like to see some fic where Asuka and whatever boy she gets with actually don't have children.

Like obviously Asuka is young & could still change her mind but it's like every single FF makes her have kids like happiness = kids or not wanting any is something to be fixed.

Still, the thing with the naming theme is a really clever little detail tho. Probably why so many ppl converged on that.
I still prefer Shinji's & Rei's little daughter from that one GOTS2 Ending.

I was under the impression that Asuka never wanted any kids.

Also, she’s going to need a lot of therapy to sort out her traumas before she even establishes a relationship with someone. Though who should she be with if not Shinji?