Kirby 2 will have security support until at least 31. December 2019, see Kirby 3 is here! – FAQs and more …
This includes our official plugins.
We can’t promise that we will publish updates beyond security issues, but if there is the need for a bug fix or feature, we may update the plugins as well.
So you can definitely keep your v2 sites running for at least a year, but of course it is always recommended to use a recent Kirby version. 