My non-expert understanding is that Futures are a specific financial instrument with set expiry dates, and are about locking in prices for these commodities at a certain date. The vast majority of these would be expiring in under low digit years. I am arguing that the ramp up time for fusion to go from "feasible design" to "having a significant impact on the the amount of oil/gas consumed" is much longer than most futures expiry dates, and would therefore have little impact.
That said, I guess people can (and do) buy futures with expiry dates for more than 10 years out, presumably they just have to find a counter party. Is this a significant amount invested? Bringing me back around to my original (and honestly asked) question: How many years out do oil/gas futures project?