As with any innovation, we'll just need to be patient.
The first step of course is to build the technology in a way that works with current aircraft without any retrofitting. That might be the tough part, but it's not unreasonable.
First off, here's the basic idea. Carts don't really need to be pushed by humans, and in fact they would work much better if they operated autonomously. On the seat in front of you, you'd select what you want to eat and drink--on an international flight, this would be part of the flight cost, so you'd just select the meal you want.
After you choose your chicken fillet and Coke, the bot would wait until the right time to start operating. It would be able to move down the aisle without any problems, likely using some machine learning that knows the whereabouts of every passenger at all times. If anyone gets out of their seat, the bots would know how to move out of the way easily.
As the robotic carts move to each row, the person on the end could hand out the food or the cart could use a simple robotic arm. The reason this could work so easily is that it's a routine, predictable environment, and bots thrive in those settings. The A.I. would know about any changes to an order, if the person in the correct seat has the right food (because of a proximity sensor in the food tray), and could chat with passengers using something similar to Amazon Alexa to make sure everything is OK.
What would the flight attendants do? For starters, they would likely need to still load the food, but even that could be automated. However, if there are any glitches or for passengers who simply don't want to deal with a bot, the attendants could assist. It would change the role of humans on the plane significantly, reducing repetition. They'd help with unusual situations, and perhaps there would be one less attendant on board (but maybe not). Mostly, they'd help with any passenger issues and if there's an emergency.
More important, you'd be able to pick exactly what you want and the entire process would run faster and smoother. You'd be able to select what you want, and the touchscreen could even show a countdown to when you can expect your meal or your snack and drink.
I'm picturing a system that is also more efficient, and the entire cart could be optimized for A.I. and not for humans--maybe it's longer and flatter, with an arm that rises up to hand out the food. Maybe it lowers from the top of the aisle. Eventually, the bot would move faster than any human, and yet passengers would barely notice the difference in how it operates other than enjoying the food faster.
Of course, there could be problems. The bot might get stuck on a USB cable or back up too far without realizing someone else wants to use the lavatory. And yet--if the technology already exists to operate cars on a hectic highway, you'd think an A.I. food cart could work easily. The A.I. is a lot less complex.
There are issues when it comes to unions and the existing workforce. Those are things that could impede progress, but it's certainly not an impossible goal. If passengers can dig into their pasta and chips faster, and the flight is smoother, what's stopping them?