What 4k video editing programs are available? So far I've dabbled in video edition with consumer tools from Apple like various versions of iMovie and occasionally using external programs like ffmpeg or Handbrake for conversion. Now I'm looking at 4k video edition but iMovie doesn't seem to support video of such resolutions (or whenever I import it it always comes in 1080p). It also seems that with the recent iPhone 6 announcement Apple still doesn't want to jump into 4k video recording, so it's not surprising iMovie doesn't handle it at all.

What non linear 4k video edition tools are available? Do I have to jump to professional tools like Final Cut? I considered iMovie's ease of use adequate and feel uneasy about purchasing Final Cut because a search for it shows dozens of courses, implying it has a long/difficult learning curve.
I can't answer your first question properly, because there are many 4K tools and you have to check yourself, which you like most. I personally like Final Cut Pro X much. But that depends on your needs.

Now to your second question:
Well, as far is I know, there isn't a 4K video editor for consumers, because normally, this user-group doesn't need 4K. So yes, you need to switch to pro-tools like Final Cut Pro X etc.