At which price do you think the world, and particularly exchange trading will switch to mBTC?
It’s obvious, isn’t it? Once bitcoin goes up in value by a factor of 1,000.

I think even now it would be psychologically easier for new people to get unboarded (especially the youth).
There’s no need to make things simpler for these softies - let them adapt, just like the old-school users did (they can’t even count past ten without a calculator as it is).
BTC is way too inaffordable for many.
But this is precisely what serves as a strong incentive to accumulate bitcoin, since it will be even more expensive later on.
Some student with $750 in BTC would have to use magnifying glass to count the zeroes in their BTC holding's number.
Let it calculate in dollars (after conversion). Also, you can always add a prefix, such as milli- or micro-.
With mBTC they would know that they hold roughly a dozen and the decimals aren't even that important.
For those who struggle with fractions or numbers with lots of zeros, just do your calculations in
sat. - that way, you definitely won't make a mistake.

I think no one would argue that in case of persistent repricing upside we *would have to* switch to mBTC eventually.
Hopefully, we won’t have to wait too long.

So why wait? Why not initiate it slowly now?
Your suggestion comes a bit late, as many wallets, for instance, already offer the option to set up mBTC (electrum).