You might not, but if Pepsi produced 90% of the demand for drinking bottles, the bottle makers might. Similarly, bitcoin companies which are not currently miners but which profit from providing bitcoin-related services might have incentive to step in. (Coinbase, Circle, BitPay, etc.)
The rational response in your scenario would be to sell your BTC and diversify into other assets.
Trying to secure the network yourself suffers from the tragedy of the commons. There is no real incentive besides altruism to not let others bear the cost of doing the work and ride on their coattails.