Bitcoin can not just die in a moment. Even if miners cease to serve the network, new ones will appear. The concept of decentralization does not die as bitcoin is not the only currency on blockchain
This is not true all of the time. There are some scenarios where this wouldn't hold up. If many (80%+) miners cease to serve the network it would have to be for a major reason. If there is a major issue with the network, or demand is rapidly decreasing, other miners wouldn't step in and start mining the Bitcoin network. If the price is crashing to zero dollars why would they? This also assumes that there are people with mining hardware on the sidelines that aren't already mining Bitcoin for some reason.
The only thing that would make something like this true is, say, if only a few miners switched off the network. If it is a small minority shutting off the miners, it wouldn't be too big of a deal. The difficulty would adjust downwards and profitability would increase for those that continue to mine.
There is a nightmare scenario where say if 90% of the hashrate were to disappear, the network would substantially slow down. It would take significantly longer to mine the next blocks and in turn, it would take significantly longer for the difficulty to adjust. This would decrease profitability for the remaining 10% of the miners and they would be mining at massive losses. If the difficulty is too high it could even be computationally infeasible for them to mine the next block. Because of this, the network would freeze completely until more hashrate was brought on board.
This is a highly unlikely scenario, but it has been postulated for quite some time now. The point of this, though, is to show that there always isn't magical miners that step in out of nowhere. Chances are, they are already participating in the network and are currently mining. There is no reason for hashrate to drop dramatically anyways though, so don't worry about it. Just keep hodling on, hash rate has been growing (and maintaining) during this bear market, and that is a really good thing! Miners have faith in BTC, no reason for them to stop believing all of the sudden. Even with a bear market.