I believe, when it comes to Bitcoin's value, one thing that isn't considered anymore, once it's boiled down to price, is settlement itself. The recipient and sender need not rely on each other if they use a different payment processor or bank to verify the transaction and settle the Bitcoin. That property can be beneficial even when the price starts to be constant. Indeed, a stable price may draw some investors away from Bitcoin as an investment and towards using it as a settlement network. Now the question was whether Bitcoin could be viable to make everyday payments, while still maintaining its decentralization and security.
A major feature of Bitcoin is that it can settle transactions without relying entirely on a third party. Transactions are verified and settled according to the rules of the network. How effective Bitcoin will be in everyday purchases will not only depend on decentralization or security. Transaction speed, fees, user convenience, and price fluctuations are also important. Users want to make payments quickly and easily for small, everyday transactions. Whether Bitcoin will remain just an investment asset in the future or will be used more as a means of settling transactions will depend largely on user needs and technological developments over time.
