Your theory is just as flawed as mine (that they'll bring out an external WinRT installer in the future) since there's nothing to back it up.
This logic flawed. Yes they have "taken nothing away", but they are clearly hedging their bets on metro for the future. Do you think win32 will be around forever? MS is moving down a very slippery slope.
MS is now only concentrating on their new "modern UI", and any apps that aren't in the MS controlled store have to be run on the "legacy desktop". The legacy desktop will probably become more and more neglected by MS. And what happens if they decide to drop the legacy in the future?
Even if that was the plan now MS does take action on customer feedback. They can't afford to drive developers away.
All this theorizing gets a bit silly at times. Like I said, people have been saying .NET is dead since 2004 all because MS doesn't come out and deny it every time someone has a theory.