That's about 9 times more than are already assigned. I assume they would extend the codespace after that point, and either break UTF-16 or create some hack with it like surrogate-surrogate-pairs.

IIRC, it was initially limited to 16 bits outright.

And yet they unified the CJK characters when they could have been individually assigned.

And didn't give a distinct codepoint to the Turkish "i" that needs to keep the dot when transformed to upper case.

I think it was a very hard decision in Unicode's part, because ISO/IEC 8859-9 (or more accurately speaking, its 8-bit counterpart) already had aliased a normal Latin lowercase "i" with the Turkish "i" and Unicode had to maintain the equivalence as much as possible.

To me it feels obvious — making them the same codepoint makes case conversions require knowing which language the string is in. Making them separate codepoints does not. The only important question is whether Turks use separate keyboard layouts for typing in Turkish and English, because if they don't, this does also make things complicated, but differently.

The unification happened because of the 16-bit restriction. I'm actually for the unification in general anyway, otherwise virtually every CJK character would have been confusable to many Z-variants.

It took almost 3 decades until the previously unassigned Plane 3 got assigned. There would be "some point" if the humanity and also Unicode continues to strive, but that wouldn't be in this century.