Bitcoin is designed to appreciate over time, so yes, the purchasing power of a single zap will continue to increase.
The amount of zaps people are receiving right now isn't significant enough to move the price of Bitcoin or have a meaningful impact on someone's savings.
At the moment, it seems that Bitcoiners are mostly zapping each other back and forth.
However, as Nostr grows to millions or even billions of users, I believe it will have a significant impact on the Bitcoin network.
For example, if a typical note starts to accumulate $5, that could dramatically shift the culture, allowing someone to buy a burger and zap the rest to someone else.
It’s going to be amazing—the combined power of Bitcoin and Nostr could truly change the global mindset.