At this point in time the effect of the supply cap is currently unknown because we have not yet experienced it. We will know what effect the 21 million cap has on price only once all bitcoins have become mined and accounted for.
Why would it make any difference?
Once bitcoin is well established(is this now?), current supply would determine value much more than future potential maximum supply. The artificial cap could have improved short term growth by creating the deflationary narrative but long term growth would require supply growth or some other incentive for new adopters to consider joining once the coin is no longer mine-able.
I can't make any sense of what you are trying to say here.
New adopters when the block subsidy ends (150 years from now?) can acquire bitcoins the same way as anyone does today. They can purchase it at exchanges, they can earn it in exchange for products or services, they can earn it from the transaction fees through block confirmation, they can steal it. A limit (or lack thereof) on the total bitcoins created has no effect on any of this.
The most elegant solution is no cap but a defined supply increase with the limit approaching zero and letting the cap naturally be set to the capacity we have to apply our technology to mining as difficulty increases. The price would continue to go up because the coin would still become increasingly rare over time and the network would still continue to grow in a similar fashion to what we have seen over a much longer period.
If you like that solution, you are welcome to use any of the thousands of inflate-a-coin altcoins that people have created because they believed as you do. How are those coins doing relative to Bitcoin by the way?
