Of course, more reserves could be discovered. One suggestion has been to pump CO2 deep into former natural gas formations, or anyhow underground - problem solved. Of course since coal and other fossil fuels also contain hydrogen, more O2 is got rid of than this, but the H2O and CO2 produced are presently not being permanently sequestered underground and hence could be used to regenerate O2 eventually, thanks to photosynthetic processes. So either way you are pushing natural limits and messing with the whole planet. This will enable energy production at current rates for 1000s of years using only known reserves of Thorium and Uranium.
Breeder reactors work.
Britain simiarly had closed its Dounreay fast-breeder in 1995. The US operated an experimental fast breeder at Shippingport Atomic Power Station in the 1970s and early 1980s. Although it showed no signs of ending its useful life, the experiment was ended due to budgetary concerns and interest in analyzing the core to see if breeding had occurred. There was a furor over cover-ups of the incident with doctored videos and incomplete reports. I too fear proliferation, but the fact is, we have no choice.