On each pricing page for Craft 2 plugins, we've been clear about our intention to stop support for Craft 2 plugins by December 2018. We're now extending this to January 31, 2019. This means, after this date, we'll not be providing official support for any of our Craft 2 plugins. Of course, each plugin will remain freely available for download and documentation will remain. No further updates will be made to plugins, and if you require support (even critical), you'll need to look to the community for assistance.
Why're we doing this you might ask? Well, there are a few factors. First and foremost, it requires the team to maintain x2 the amount of plugins we have on offer. This takes up valuable resources that could be better used on newer and better things.
Secondly, we're drawing a line in the sand to assist in the push for new sites, and hopefully existing Craft 2 sites, to make the switch to Craft 3 which is better, faster and safer. If you aren't already, the announcement of Craft 3.1 should certainly let you know that Craft 3 is the future and a platform that'll continue to grow and improve.
Until the January cut-off, we'll continue providing support for Craft 2 plugins, but we've always prioritised Craft 3 support.