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.

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.

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.