There's been a proposal to bury them not-so-deep, but saturated with salt to prevent decomposition. It's not necessary to sequester the carbon forever, just on a time scale for natural absorption of the CO2 into oceans and then into carbonates (which is something like 100,000 years, IIRC).
No, by then it's at least conceivable that cold fusion will by then be a
reality. If an individual cracks this problem maybe they'll offer a paper ending with a comment akin to Watson & Cricks 1953 paper on DNA. "It has not escaped our attention that ..." Or words to that effect.
