On the current schedule, SDKv1 addons will continue to be supported in all releases up to around June/July, when the next Long Term Support (LTS) release will come out. That LTS release will continue to support SDKv1 addons, and will be officially supported for 18 months. So official support will continue for around 2 years from now. You can even continue to use that LTS release past the end of official support, but it won't be updated nor will we provide support for that release any further beyond the end of its 18 month support period.
The latest release allows auto-updating addons from the Addon Manager, so install any available updates as many addons may have already been updated for SDKv2. In some cases there may be alternative addons or features you can use instead - for example perhaps Advanced Random can replace BHT Smart Random, perhaps you can get rid of jQuery, File (WebView2) is now replaced by the built-in File System plugin so you can likely replace that, Greenworks is superseded by Steamworks but also the latest version of Greenworks supports SDKv2, Valerypopoff Ease could be replaced by the built-in Tween, etc. Failing that, contact the addon developer for an update.