As an incentive to keep the miners online, the community can increase the number of Bitcoins to be mined. So how do we increase the number of Bitcoins?
I think the solution is to a fixed exchange rate for old Bitcoin from version 1 to version 2. Where the exchange rate is voted on by the community.
The analogy in the real world would be a stock split. Microsoft had split its stock several times in the past. We can copy the methodology. For example, if we want to increase the number of coins from 21 million to 42 million, then we can do a 1 to 2 split, where as each version 1 of the coin and exchange for 2 version 2 of the coin.
If Bitcoins is truly useful and is widely adopted in the future, then there would be no problem for version 2 Bitcoins to retain its fiat exchange rate. Usually following a stock split, the underlying stock price increases.
There will be philosophical and technical challenges.
1. Should we increase the number of coins to start with?
2. How to modify the software?
"the exchange rate is voted on by the community"
That is what democracy plus a fiat currency is, a majority votes for the guy/girl that promises to give them everything their heart desires for free and ultimately the currency is driven to zero value as finite resources collide with infinite desires. Guaranteed disaster.