1. This is a problem for micropayments but any global decentralized system has a fuzzy notion of synchronization that requires a 30-120 second lag at this point. For example, compare how many orphaned blocks BTC creates to how many LTC creates. Maybe 10 minutes is too much, but 2 minutes is too little. I don't see changing much in the future barring A Breakthrough (TM) because as the internet grows, lag-per-bounce slowly creeps down (with physical limits given by switch reaction time and speed of light / EM field in copper wires) while the number of bounces should creep up (logarithmically in the size of the network maybe? I'm assuming that the internet is roughly tree-like). As reserve / settlement medium, this is not a problem.
This is exactly the point to calculate the value of one bitcoin when it accounts to let's say 5% of all money transactions in the world. You have 21mio. Bitcoins which is like the cash of dollars, euros etc. So you have to set the 21mio. relative to the cash in the world not all the fiat. (M1 or even M3)
There are about 800billion Euros. The Euro is mainly used in the EURO-zone which accounts for around 20% of the eorld economy, so about 4 trillion US in cash in the world.
1% of all transaction would mean a market cap of 40 billionen dollar so 2000$ for each bitcoin.
5% lead to 10 000$.
10% to 20 000$.
It might be higher: M1 is about 7 times more than the cash. M3 is 15times higher. The numbers above assume the same with Bitcoin but depending on regulation the reserve of service (visa like) would be higher. So maybe they have a 25% reserve so this would lead to 2times higher prices. Another point is, that many bitcoins might be lost forever and we have only 16mio. coins in Jan. 2017, 18.5mio. in jan 2021. Bitcoin could be seen as a store of value, too and maybe other technologies which may affect the price.
It might be lower: Maybe even if people use it they might see it as risky to hold btc depending on the volatility when it is adopted. Because of that and because money can be transfered much faster then bank wrie the the velocity of money might be higher. So this means that it feels like the supply of bitcoins is higher and therefore its price lower.
For both: sure depending on the amount of transactions it will be higher or lower.
PS: These are just very round numbers and might be of by the factor of 1.5 or 2. Consider this.