You are right, it has been a while. The reason I stopped working on it was because of a multi language Kirby bug. Maybe it has been fixed now, I have not tested it yet: Really strange behavior that makes Kirby save to wrong content file
Now there is a development going in with Kirby 3. You can buy to get more information about that with https://getkirby.com/next
I can’t tell you anything on what it will be, but the changes are so big that I need a complete rewrite of Kirby SEO, which I had already planned because of the ugly code. It might not be good news but instead of building two plugins from scratch I will wait until Kirby 3 is released and build the plugin from scratch to that version only.
If you still want some progress with the current version you can add pull requests and also write comments on each others pull requests if they work or not and I can just approve them.
Anyway, if I get the time, I should be able to start over with the new plugin before Kirby 3 but that will be to clean up the plugin core and nothing around the field itself.
I expect the new version to be released in the mid or late 2018.