I've seen this same discussion for over 10 years now. Nothing has changed, things have only gotten worse for Linux. Usage has only increased for home/hobbiest/developer users. And I've seen a few Linux environments replaced by MS stuff, but never the other way around. And in the last 5 years even the server market is slipping to the MS side...see you in 10 years : )
I truly believe Linux has it's place in the IT world, but as long as it remains Open Source it will be Closed Doors to the IT market.