You can be sure that as soon as Microsoft drops support for Windows 7 that nefarious actors are going to go wild trying to find (and, I'm certain, actually finding) new vulnerabilities to exploit because they know there will be a huge base of Windows 7 computers still out there. It will be a relatively short term frenzy of activity to strike while the proverbial iron is hot.
Those who do not go to Windows 10 are likely to be hit, repeatedly and rapidly, with hacking attempts of various sorts. Whether that succeeds on any given individual's machine is not relevant, as something thrown will eventually pierce.
I don't care what OS you use, Windows, Linux, or anything else, but it is insane to use an unsupported OS as a daily driver. And by daily driver I mean connected to the internet and doing things like web browsing, e-mailing, etc.
I still have a Windows XP laptop that I've kept because of one piece of now-ancient software that I don't even want to think about trying to figure out what would be required to port it to a later Windows. It hasn't been connected to the internet in over a decade now. The same will be true of my Windows 7 laptop unless I decide to play with dual booting and putting Linux on it. It's an old ASUS machine that will not upgrade to Windows 10 secondary to some hardware incompatibility (and it's the upgrade process that announces this and won't even let you continue). If I go that route it will only be the Linux side that would be allowed to connect to cyberspace going forward.