I hear more and more by people that they consider bitcoin more of a store of value (eg, gold replacement) than as a currency, especially as the transaction fees go up. I have also heard many people say that even if bitcoin is only used as a store of value, and not as a currency, it has utility.

But this is not sustainable. Imagine bitcoin prices continue to increase and eventually all the coins are mined. There are not many transfers because people are mainly hoarding. Thus not much transaction fees, which is the only source of income for miners. Hash power reduces dramatically, and so network security deteriorates.

It seems to me that the only solution would be for bitcoins to be perpetually made available (no limit at 21 million).