It's possibly one of the questions people like you and me wonder about every day, well, whenever we don't feel like working and try to go into the clouds for a bit. Will there still be airplanes? Will there be spaceships? Will there be neat teleportation devices or trains that travel with the speed of light (keeping in mind that just a few days ago the new speed record was made, just over 600 kph), or maybe we'll be thrown back in time and for a sake of green thinking we'll switch back to some sort of some massive high speed hot air balloons. I have no idea. Based on history though, it's more likely that the hot air balloon version won't be the main thing, even though I doubt it will go anywhere either. Based on history things will only get faster, bigger, better, hopefully also greener, but we never know.
Just to remind us how the travel industry has changed over time, Travel Campaigner featured an animated video by My Voucher Codes about how people have booked their holidays in the past, going back to 1960s. And, if you weren't born yet and don't know what 60s look like, well, many people who did live through 60s don't remember a thing about it either. But in case of travel, people actually had to go to a local travel agency to book a holiday. You can still do that today as well but back then it was pretty much the only way to do it. Obviously also the modes of travel were different - boats, buses, trains - were the main modes of travel. Air travel started to become more popular in the 70s. Eighties brought us the cruise industry as you know it today - with the rising popularity of air travel, cruise ships had to add some added value to their packages as speed of travel wasn't really their thing, and they became floating entertainment hubs.
Since the 90s travelling has become a lot more affordable, finding and booking the trips a lot easier, and the choices...well, you can pretty much go anywhere today.
You can see the animated video below -