I think old power tools will increase in value as time passes. It's not the antique value, but rather the fact that they no longer make affordable decent power tools. For example, have you tried to find a power drill that stiill uses a key in the chuck lately? Good luck, they almost all have those hand tightened chucks. Try to drill thru a piece of heavy steel with one of those, and you'll soon find that you can not do it. You'll wear the flesh off your hand trying to tighten that damn chuck, and will finally be forced to borrow or rent an OLD drill with a key, or take the job to a metal shop. Those hand tightened chucks are a complete joke adn are useless. Personally, I consider these so called "tools" are really nothing more than TOYS.
On the positive side, you can still buy keyed chuck drills, but be prepared to spend a fortune. The top name brands such as "Milwaukee Tools" still are made with keyed chucks, but they are pricey. For a professional, they are worth the cost, but not for the average homeowner doing a few repairs. This means that you must either find an old drill at a garage sale, or just rent a drill from a local tool rental place.
And these battery powered tools are even worse. In fact I refuse to call these things "Tools". They are and always will be nothing more than "TOYS". They work great for a 12 year old kid wanting to build a birdhouse. Try to use these on a serious home repair project and you will likely do what I did with mine, which is toss the goddamn thing in the garbage. If there's anything more frustrating than trying to finish a job and the damn tool runs out of battery power, please let me know. Unless you have at least 3 batteries for each tool, and the desire to keep running to a power source to recharge batteries, forget them. They're worthless. You may as well just run a cord from the power source and use a plug in tool to begin. I dont care if they are a 6 volt or a 24 volt tool, they all lack power and all need constant battery recharging. And prepare to go broke buying batteries. The batteries normally cost nearly as much as the whole tool. Sure, they are handy when you have to go across the road to attach your rural mailbox to a post and it's too far to run an extension cord, but face it, you're putting in four screws. Try to put in 400 screws and you'll be running back to the house at least ten times to recharge batteries. Worse yet, you will NOT find a battery drill with a keyed chuck, period.
It seems that each and every day I am learning to appreciate the old power tools from the 1960's thru 80's more and more. I do my best to keep them in good condition, because in the future they will become more and more valuable as the supply vanishes from garage sales and auctions. When all the junk tools from the 1990's and 2000s are long buried in garbage dumps, those of us with the older tools will be lucky to still own them.