I like your bullishness but I think we're still far off from BTC hitting 1 million, ie. I think there are more pressing matters that should be solved first.
6 months go I would have agreed absolutely, but it's pretty crazy out there. It may take 5 good years to get another fork in place.
As I mention in the latter part of my comment, I'm rather positive about a precision update being less debatable than a block size increase. On the other hand you're not wrong. It's indeed something that could be worth looking at rather sooner than later. But in my opinion 5 years for getting a hardfork in place is still way too pessimistic. But who knows, there may be some nuances to the problem that are not obvious at a first glance.
Without having a proper scaling solution widely deployed anything below 0.0001 BTC is effectively impossible to transact. In my opinion thinking about increasing decimal precision will only make sense once we're close to making dust transactable again.
Lightning is round the corner. Next year it will start being used properly. I think we're very close now. And there is nothing blocking it's implementation. It's definitely coming.
I also think that lightning is very close now. But the timeframe from "very close" to production ready to the actual deployment and real life usage may still be 1-2 years away. I will be gladly proven wrong though.
Once we're there my educated guess would be that such a fork could be deployed fairly undisputed, as I don't see any reasons for contentious camps about decimal precision arising, making it easier and thus faster to deploy. Then again crypto is a weird place, so who knows what counter arguments against an increase of decimal precision arise. It would be interesting to see how much the effective impact on block size would be, for example.
From memory there was a very specific data related reason why bitcoin was capped at 21 million.
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The technical reason is the size of the integer datatype that Bitcoin is currently using, OP is suggesting to use a larger integer datatype instead

Once we're there my educated guess would be that such a fork could be deployed fairly undisputed, as I don't see any reasons for contentious camps about decimal precision arising...
Decimal Point Rising....
A movie title?
nice catch

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Can it be done as a soft-fork ?
I too would love an answer on that question.