Next they'll be saying, Bitcoin will be the interplanetary reserve asset. Then the interstellar. Intergalactic. Universal. Not in our lifetimes, is course. But it's coming.
The base layer consensus protocol would run at decade speed and would just be used to net out long-term/long-distance differences; most transactions would be on higher-layer systems that settle faster. Charles Stross explains this stuff in Neptune's Brood.