Meanwhile, as bitcoin gains popularity, those bitcoins will be worth more of your local currency, and more fees may be collected. Right now the subsidy is significantly higher than the fees.
This is what I fear the most - that in the future bitcoin's transaction fee will be so high that sending BTC would be more expensive than using other payment processors.
Currently standard transaction fee is ~20k satoshis (and it's growing) it is roughly $0.20 ATM. In the future BTC might be used only to send very large sum of money (hundreds of dollars equivalent or more)
Bitcoin microtrasactions will be impossible.
There are two possibilities...
ONE
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The transaction capacity of bitcoin is increased (for example by increasing the block size). This will allow more transactions to be confirmed, so the fee won't need to increase as much. On-chain transactions will continue to be affordable.
TWO
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Third party providers will create "bitcoin banks". These will be businesses where you can send your bitcoins, and they will secure them for you. Transactions between members of the same "bank" will be able to send to each other quite cheaply since it will just be a record to update in the "banks" centralized database. Transactions between members of different "banks" will depend on the agreements those "banks" make with each other. The banks will notify each other about inter-bank transfers with a system similar to the current ACH or SWIFT systems. The banks will settle up the differences between them on a regular basis on the bitcoin blockchain. Therefore the only "on-chain" transactions will be settlement transactions moving a very large sum. A fee of $100 or $1000 per transaction might be quite cheap for such large value transactions. The "banks" will share this cost across the millions of transactions that they perform, so the cost per off-chain transaction will be quite small.
(Note that such "bitcoin banks" already exist. Coinbase is exactly what I'm talking about. They allow you to send your bitcoins to them, which they then secure for themselves. Then they provide you with an "account" in their system (which is really just a record in their centralized database). If you send to other Coinbase users it is completely free, since it is performed off-chain and they are just updating records in their own database. If you send to non-Coinbase users, then Coinbase will package up your transaction along with the transactions of others that occur at about the same time. They'll send a single transaction that makes payment to all the intended recipients during that time. They'll pay a single fee on that transaction, and split that cost across all the transactions that were packaged together. Since it covers multiple people sending, it is quite cheap per person and they can afford to pay the fee for you in most cases.
