I doubt if Bitcoin could even cover the transaction volume of a small country like Zimbabwe at this stage, so scaling Bitcoin to become the global reserve currency will be a challenge. We will have to accept temporary solutions like the Lightning Network to accomodate for larger scaling options.
Simply increasing the block size, will not scale enough to become a global reserve currency. ^hmmmmm^
Governments will rather opt for private Blockchains with better scaling solutions than using a public Blockchain where they have no control. ^hmmmmm^
again bitcoins mainnet should not become a reserve currency as thats just pushing it into the background and using LN/crapcoins as the front-end.
as for saying bitcoins mainnet cant scale. and then twisting the plot to suggest that if it could scale it would still be a reserve currency in the background is foolish.
bitcoins mainnet can scale as a front-end payment network, but you need to wash away the failed doomsdays scripts you may have read that it needs XXgb blocks by tomorrow.
instead put a rational/logical hat on and realise that bitcoins mainnet should make baby steps forward periodically to expand naturally.. we are not gonna get 7billion people in a day.. its a years-decades scaling not a one day superman jump to extremes.
these safe onchain scaling babysteps should have happened last year. but instead it has been halted using fear of superman flights.
analogy:
yes babies should not take thier first baby steps because mummy and daddy fear the baby will run into a car withinin 10 years. so lets fearmunger all parents that all babies that take their first step will guarantee to run into a car tomorrow. so wrap up your baby and tie it to a cot. and call it your reserve baby. and then adopt a second child to be the one you push around the streets
also wash away the concept that bitcoin will become the 'one world' currency' for 7billion people.. instead think about the current 0.0266% using bitcoin and imagine it settling at about 1-5% of world population(after NATURAL not SUPERMAN growth). definetly dont assume 100% uptake. as that then becomes no 'free choice' option if its the only one.