Honestly, I don’t think things are likely to change much for the next several decades. Maybe somebody will come up with a workable business model for providing supersonic or hypersonic transport for those well-heeled enough to afford it, but there’s really very little market-based incentive to do so, and the environment impact of such operations is bound to be appalling even in comparison to current airline operations.
Most of the past half-century’s innovations have been in the areas of efficiency, capacity, and safety. We’re close to the point of diminishing returns in all three of those domains. Large amounts of money are needed to achieve incremental changes in any of them. Short of some disruptive technology on the propulsion front, I seriously doubt there’s much more that can be done to make a substantial difference in the economics of aviation.
The basic design of airliners is pretty well settled these days. Wingspans have to fit within existing runway and taxiway infrastructure. Terminal boarding and off-loading provisions are adaptable to a reasonable range of aircraft heights and lengths; the Airbus A380 drove quite a few airframe-unique accommodations for both aircraft access and high-volume passenger processing that gave some would-be host airports pause.
The only really new configuration that keeps getting touted as “the future” is the Blended wing body concept, but I think that would suffer significant challenges in terms of being able to be handled without large-scale investments at the destinations they’d want to ply. The people saving money operating that type of aircraft wouldn’t be the same people called upon to invest in providing for them, so introducing something so radically different could be a very tough sell.
International air travel became the go-to alternative to ocean liners because of the gains they offered in both time and convenience. The original Queen Mary could carry just shy of 2,000 passengers; about five Boeing 777s could handle the same number of travelers over a comparable distance in a tenth of the time. You just aren’t going to see economically viable aircraft/spacecraft offering a similar order-of-magnitude advantage for the foreseeable future.
For that matter, hypersonic travel itself may ultimately achievable, but it might very well be accompanied by a bit of the glamour (and frisson) that went with air travel in the 1930s — comparatively fast, ruinously expensive, and carrying with it a teensy possibility of occasional violent death for its participants. If that aura doesn’t wind up being attractive to potential investors or passengers, the technology underlying hypersonic transports is going to have to be a lot more reliable than it has been to date.
The Aircraft Obsession 