Yes, lending bitcoin will be disincentivized because since there's no supply of new bitcoin, eventual defaults are mathematically assured.
Instead of lending rates, perhaps there will be fluctuating rates of equity-for-capital. That is, the purchasing power of bitcoin will increase with greater general productivity growth, and will decrease with lower productivity growth. As a bitcoin holder, if general productivity growth is slow or negative, you'd be incentivized to accept less equity in a business per unit of bitcoin buy-in. If productivity is growing quickly, you'd demand more business equity in exchange for your fast-deflating bitcoin capital.
Makes intuitive sense: if there isn't much innovation or population growth happening, then it will become cheaper to get capital in exchange for equity. A naturally competitive dynamic.