I don't think they need to worry; AWS continues its potato quality UX with CodeCommit. Unless you're hard core into using git in terminal for practically everything I can't see this taking much if any business from the existing big players.
That's a pretty bold claim. Do you have any data behind it?
It's only anecdotal but in my experience it's almost the exact opposite; having worked in multiples of both MSFT and non-MSFT shops it seems like almost every one uses a UI to handle git. I don't blame them; it's not always easy visualizing all of the changes (in my opinion at least) just through a terminal window.
So I suppose I shall digress and admit I committed a total failure at an internet statement on a decently technical forum.
in the words of Homer....
doh!