Sure. But the rate of BTC issuance is already the lowest rate of all commodities. So, most of those 100 years will be just the tail end of issuance.

Fiat nominated debts are beside the issue. If you take a fiat loan today, you know it will be cheaper tomorrow. Interests on BTC nominated debts are not sustainable on the long terms. If you take BTC loan today, you know imagine (to use your own words) it will be exponentially more expensive to pay back. 

The only way to pay it back properly is to decouple btc from fiat, and then we go back to my argument; given issuance rate halves every ~4 years.