Oh in the end?* None of them.* I believe that the GUI Desktop
  metaphor is coming close to the End Cycle.* I forsee the
  replacement as something *very loosely* akin to - an immersive
  environment not tied down to Documents, Files, Folders, phones,
  movies, TV, cameras analogies/metaphors. The line will blur and
  disappear between video, typing, voice, pictures, as I think it
  will be possible to receive information in the format you most
  desire. I think the emphasis will be on "views"; what you
  receive will be customizable depending on your skill level so
  that there are no barriers to human/computer interaction.
  Someone who is 7 years old will equally be able to customize
  their experience to their needs and skill levels and primary
  mode of communication equally well as a 42 year old computer
  programmer, or a 22 year old game designer, or a 70 year old
  grandparent. a) You have a preferred mode of communication.*
  Visual, auditory, mathematical, musical, tactile are the big
  three, but there are others.* There's logical thinkers,
  emotional thinkers, introspective thinkers, etc and they all
  interact with themselves and the world differently. b)* If your
  preferred output is spoken words, you would have the option to
  speak and a set of powerful translators will be able to not only
  save your content as you provided it, but it will be saved in
  all of its forms, some parts translated into different modes if
  it needs to complete the set. If you are the recipient of your
  work, you will want it back in your preferred mode of
  reception.* Example: You might like to speak to get things OUT
  of your mind, but you prefer to READ to put things in. If
  someone else is the recipient, if they prefer video, then they
  could get a video of you talking - *if* you give permission for
  that, that is. If you wish to convey your exact words, you can
  have that done. But if you wish the *idea* to come across, the
  computer will be able to translate that into analogies that,
  with your approval, would be transmitted. Example: If someone
  understands things better in a line drawing cartoon form, your
  ideas will be translated into a story told by line drawn
  characters conveying your ideas.* It might not even contain any
  words; and of course you will have the ability to modify it
  before sending off to be sure it conveys you correctly. You will
  also have the ability to place *your* style of logic into the
  system itself so it can perform tasks in the ways that make
  sense to you. In other words: Programming willl be a key part;
  but something akin to a much upgraded future version of the MIT
  SCRATCH project; an extremely powerful visual programming
  environment, aimed at 9+ but being used even by people who are 5
  and 6; and some of the things created rival commercial games;
  precisely because they were given a set of basic but powerful
  tools to automate the tasks necessary in a game, in a way that
  makes sense for their way of thinking. I'm not saying that
  Minecraft itself is the model; or that things will be
  programmable blocks (although I imagine the first iterations of
  a concept like this will start out that way), but rather, the
  idea of have a combination of Object Oriented Logic style logic
  flow, ALONG WITH something they keep TRYING to get rid of out of
  programming but really works more like how our minds work: The
  GOTO. Akin to a teleport, it allows you to jump to any part of a
  system at any time that is necessary;* It is akin to a click on
  a hyperlink on the WWW; where you are not limited to containers
  within containers inheriting features but the ability to jump to
  ANY part of a system just as our mind jumps from analogy to
  analogy, almost seemingly randomly sometimes. Immersive, virtual
  3D, no limits to the kinds of control you can have over what you
  input, how you receive feedback from the system, and what the
  internal processes are that you wish the computer to perform,
  and when. So "who will win?"* I suspect a dark horse will emerge
  that will blow them ALL away AND they won't see it coming. It
  will be easy enough to for a 4 year old to use; sophisticated
  enough for anyone to be able to make the Interface look and feel
  the way they wish and powerful enough to do anything with
  anything. Example: If I wanted my computer to behave like Tandy
  Deskmate from 1990, I could set it up easily like that. If I
  wanted to use long forgotten VAX/VMS typed commands to operate
  the system, I'd be able to do that. If I wanted to stick with a
  desktop metaphor because I'm comfortable with that, I could do
  it. If I wanted to create the Inside of the TARDIS and operate
  my computer from within there, I could do that. There would be
  no file saving per se; more like a state system which allows
  infinite undo and returns to any point within the system. Too
  many constraints in all of the systems currently available.
  Sorry I couldn't give you a simple answer; I'm 42; got my 1st
  computer at 11 yrs old; and as awesome as the changes have been
  through the last 31 years, some of the changes haven't been
  good; and a lot lot of it, ,basically hasn't changed at all.*
  Human/computer interface has bothered me from the beginning; I
  work within whatever I find myself facing; but there's a lot
  that needs to happen.