If the rebate pool runs out in 100 years, then the Plutons in circulation will still remain in use the same way as they were before. The only difference being that new ones will not be created. Emission is set to reduce by 0.1% when the Bitcoin conversion on the app starts moving above 5 Bitcoin. This means that the higher the volume on the app, the slower the emission. This means that it could theoretically slow down to hundreds of years more.