Noticed this Popular Mechanics article, where Air Force Chief of Staff Dave Goldfein suggests a future tanker will operate in low-Earth orbit. Perhaps this is because the new B-21 bomber will operate there?
From the article: Then again, money might be less of a consideration than we think. In his interview with AvWeek, Goldfein remarked that his next generation tanker could “operate at low-Earth orbit” and that while it might sound “a little bit odd” for him to discuss a future tanker with Air Force Space Command, it makes “perfect sense.” What he means is anyone’s guess, but here’s a stab at something that could operate along those lines: a tanker that could stay in orbit for months or even years at a time, much like the X-37B spaceplane, and then descend down into airspace to deliver fuel to friendly aircraft before accelerating back up into the relative safety of orbit again. Whatever the case, it sounds exciting…and expensive.