Re: What will be BTC price when it reaches 1 billion users?
Any thoughts? It will be higher or lower? 
Your question seems a bit illogical.. ( Or too logical
) Ofcourse the price is going to be higher if more people use it. Less supply (people will keep losing coins over time) and more demand/people that want to have/use it.
I however am interested in seeing how Meltcalfe's law works with cryptocurrencies, ( defining the value of seomething based on the amount of users it has). (If it is applicable at all here.)
I was wondering if the scalability gets solved until there, how this will affect BTC price...
The lightning network has the potential to solve scalability issues. We just need to wait for the devs to make it easy and stable enough to use.
If you're interested you can read more about it here: https://lightning.network/