Well, if you want to have your say on what you think should go into WordPress 4.4, now is a great time.
WordPress 4.4 release lead Scott Taylor has made a call for wishlist features on Make Core. So, you can comment on the post and make your greatest desires known.
As you consider what you want to see in the release, I'd first advise you check out current features as plugins and their status, as well as the list of available components and their owners. Sometimes, it's easier to work with the plugin or component owner to get your viewpoint listened to.
Otherwise, Scott's post is a great place to have your say. There are already dozens of responses and a lot of good ideas. Calls for REST API inclusion, term meta, shortcake (shortcodes), and the fields API are mentioned a bunch. But there are many other really good ideas.
I know Scott already has a working list of things from this post and elsewhere that he'd like to see in the release, and it's a pretty big list. If half or even a third of them make it, it'd make for an incredible release.
Personally, I think it's also a good time to peruse through the official WordPress Ideas board — there is some good stuff there.
There's no rest for the wicked; WordPress 4.4 is underway. Onwards and upwards.