As for AA batteries, they have been around since 1907 (though the size was not formally standardized until after WWII).

I wouldn't be surprised if they were still around in a few decades' time - there's simply too much cheap consumer electronics out there relying on AA for it to make sense to introduce a new standard. (Energy density is likely to keep increasing - but as for the form factor itself, I suspect it will outlive me.)

But both are trivial to create adapters for as long as you have a suitable source of electricity.

Unless everything (finally) goes wireless.

Even then there will need to be receivers that tap the wireless power source. To make that hard to regulate to a suitable current is exceedingly unlikely. Unless the device is extremely sensitive, if you can get any kind of electromagnetic power, converting it to electricity at a reasonable voltage might not necessarily be quick and easy if no current tech is available, but it's the kind of thing you can achieve from near first principles in the garage with some basic tools and a spool of copper wire.

But that's only necessary if you can't get hold of a source of electricity (such as a wireless receiver) and a voltage regulator of some sort (likely to exist as part of said wireless receivers).

In the past we've had problems recovering data from magnetic disks and the like, but powering ancient devices with simple power input requirements have not generally been very hard, and it's not likely to become so anytime soon unless not just every computer but every lightbulb, kettle, electrical oven and every other little appliance suddenly start receiving energy in a fundamentally different way.

how about a solar panel on the back (or a transparant one on the front). How about heat activated. How about activated by radiation in the air (microwaves).

Absolutely