There is a simple answer to the question and an alternative.
The simple answer is that if you want to stay with Windows, eventually you will move to Windows 10. There is no long term alternative, hardware will break, with no source of replacement except 10 and those replacements will not have driver and third party software support for earlier versions of Windows. If the hardware doesn't kill you, the software will, unless you are prepared to run obsolete versions with no support other than yourself.
If you don't want to migrate to 10, for whatever reason, you need to make plans other than Windows. The problem with running Windows 7 after the end of Microsoft support, will, if anything be worse than the XP to 7 conversion. 7 is still very popular across the Windows install base, by some reckoning, it's still the most prolific - but you know what they say about statistics! There are more similarities in the code base between 7 and 10 than there were between XP and 7. The reality is, that when Microsoft describe the vulnerabilities patched in the latest 10 update, they are also giving a very strong clue to the bad guys where to look in 7. And with 7's expected remaining base, that is still a better (bigger) target than MacOS or Linux.
I'm not intending to migrate to 10 for my own use. I will maintain a 10 machine for "Family Support" - yes, I know - but some of those won't make a change.
I will keep a Windows 7 machine for those things that Linux doesn't (and won't) support. Presently, that is my Canon Scanner, with positive/negative film capability in the lid and my trusty Adobe Acrobat Pro (Version end of life long ago but still capable of all I need, like generating fillable forms. This machine will not connect to the internet, those two functions don't need it.
I switched my daily use machine over to OpenSuse Leap Linux, with the KDE desktop, about three years ago and I'm very happy with it. Why that particular Distribution? I toyed with SuSE Linux 7.2 Pro some 15+ years ago, when Linux was far less user friendly than it is today (think dependencies and drivers) and since my then employer was mainframe and Windows based, I just didn't have the time to get into Linux but the distribution stick with me. It's now very user friendly, just boot the distro DVD, answer a couple of questions, let it do its thing and 20 minutes later, you have a fully working system, with all internal hardware recognised. There a re other distributions and desktops just as easy too use but I'll leave it to their fans to advocate their benefits.
OpenSuse Leap is not a bleeding edge distribution, if you want that kind of thing, go for OpenSuse Tumbleweed. Leap is based on the codebase from Suse Linux Enterprise, SLE, the commercial enterprise grade version and is extremely stable, you ISP probably uses that or Red Hat Enterprise Linux (RHEL) for their web servers.
The biggest difference you will see from Windows is in the update process (I'm speaking about Leap here). It uses a continuous upgrade model, with only a "MS Feature style" update once a year. You can decide whether to take the upgrades of not, I'm comfortable with taking them all. The vast majority do not need a reboot after installation, Kernel updates do but there is no pressure to do them until your next planned reboot and they never forced on you. Why Microsoft don't adopt a similar strategy, only they know! Any security exposures identified are usually fixed within hours or days, rather than weeks or months. Linux is inherently more stable because it was always designed as a multiuser online system, normally run in non-elevated status.
BUT and istn't there always a "But", it isn't Windows; the interface while similar is not identical. That is enough to deter some people and that's fine but really, any of the popular distributions require only a small learning curve to get started and you build as you go along. If you made the transition from Win95 to XP, you'll be fine.
There are open source applications equivalent to most of those in Windows but again, equivalent, not identical. For example, while LibreOffice provides all the functionality of Office Professional, plus a bit more, the interface is more akin to pre-ribbon days and the Macros, while similar, are not compatible and will likely need rewriting. Again a small learning curve. Some applications are compatible between Linux and Windows, for example, Firefox, Thunderbird, VLC Player, Audacity, etc, though some may use a different internal file structure, Thunderbird, for instance.
If you have Windows only applications, there is WINE that provides a Windows-like environment to allow them to run, for example, Irfanview or Lotus Smartsuite (don't ask!). There is a commercial version, CrossOver Office, that will run MS Office and installed versions of Photoshop among others. Note that you still need licenses for them to comply with their EULAs. Note also these products do not work for drivers.
One of Linux's strengths is the range of fora, where people are always willing to help and the historical questions and answers can get you going if you get stuck. Google is your friend in finding answers.
Is Linux an adequate replacement for Windows? My experience says yes but remember what the "P" stands for in PC.
What about other alternatives? Obviously, there is Apple, with their Macbooks and Mac Pros. Their infrastructure is more tightly controlled than Microsoft. Personally, I'm not prepared to pay the premium prices for essentially similar hardware but if you want to move to MacOS, that's the entrance fee. I'll leave it to others to explain why they are the best thing since sliced bread.
What else? If you love your Android phone, you could consider a Raspberry Pi, build your own machine and run Android on it. It's possible; whether it's wise, I leave up to you!
And finally, for the brave of heart, you might want to take a look at the ReactOS Project. Very much still in development but the general aim is to develop an open source operating system that supports a Windows environment. Google it. Last time I looked, the project documentation looked pretty good. Up to you.
To wrap up, I'm moving to Linux on my remaining Windows machines by end of support date. I'll keep one offline Windows 7 machine for things Linux doesn't support and for translation of any incompatible file formats (via thumb drive). I'll maintain one Windows 10 Pro machine for family support.
Good luck with whatever decision you come to.