If you wait too long to upgrade, you'll end up having to pay for it instead of getting it for free if you upgrade now.
I seem to remember similar threats regarding Win8. I saved my $30 and have not yet regretted it.
Waiting until Windows 7/8 go EOL is only going to cost you money. What's going to end up happening is that Microsoft is moving to the walled garden model of software distribution the same way Apple does it so if you go to Linux or any other operating system, you'll be missing out on most software releases. You can bet Microsoft will be pressuring developers to release software on Windows only and not Linux if they want to sell to Windows users through Microsoft's online store.
You know, I don't think MS wants me as a customer anymore. I hate to say it, but I think I might finally be crossing over into the non-mainstream. So maybe I don't want MS to provide my OS anymore either. For me, it just means I learn a new OS. For MS, it means they lose the enthusiasts and hobbyists that made them who they are. So, who do you think will win this race to the bottom? MS or Apple? From what I can see, Apple has a 15-year head start. Not only that, they at least feign value their supplicants' privacy.
I might humbly suggest that Apple has been wallowing with the pigs for the better part of two decades and MS doesn't even know where the sty is located. My evidence: Zune and Win8. Win10 is at least ten years late to the party if they wanted to capture the 'tard market. In this horse race, my bets are on Apple. The market MS is targeting with Win8/8.1/10 is not their primary customer: corporations and businesses. They've already lost the mainstream customers and won't be winning them back without a complete rebranding.
I've said it before: MS has opened a chink in its armor and allowed the opportunity for a new competitor to emerge. That Valve is not taking advantage of this blows my mind. If ever there was an opportunity for Steam to gain traction as an OS, this was it.
I intend to evaluate Win10 and decide if it is worth my time and trust. If not, I'll back off to Win7 and figure out which flavor of Linux I'll be using instead. I value my privacy more than I value ease-of-use.