IBM manufactures lots of hardware, produces new technology it licenses, and has an enormous software consulting division. Microsoft does none of these things.
If anything, Microsoft will become like Computer Associates (CA Technologies), a company that milks products enterprise is hooked on and can't quit, squeezing money out of these things for decades to come.
Office (especially Word / Excel / Outlook trifecta which practically everyone uses at work for documents, scheduling, e-mail)
Lync (text, voice, video chat that is integrated w/ Outlook contacts)
Sharepoint for intranet portals, content management, collaborative documents with version control
Dynamics ERP & CRM for accounting and sales
SQL Server, which has a sophisticated BI stack for reporting & analytics
Visual Studio for developing custom applications that can interface with the APIs of all above products
Now they have or are working on cloud versions of basically all of these products so you don't even need any hardware if you want to go that route.
Personally I am not a huge fan of Microsoft for a lot of reasons, but no other company, including IBM, comes even close to offering such a comprehensive enterprise stack. They're the only company that has a product for everything (except hardware).
So the less people use Windows the less appeal there will be for these products. They are all anchored to the same sinking ship.
Also, SharePoint sucks. I had to say it. It's a worst-in-class product in a sea of vastly superior web application and document sharing platforms. I can't believe you included it in your list. I severely dislike many of those other products (Outlook, Exchange, and SQL Server, specifically) but even I'll admit that those products actually do what they're supposed to. SharePoint is nothing but a black hole where documents, time, and energy go in but nothing useful ever comes back out.
* It runs on Windows and carries with it all that baggage... An unnecessary GUI is always running. Endless security issues. You'll need to reboot regularly to apply patches. You'll also need to deal with things that are unnecessary on other platforms like antivirus packages and--because it comes with that aforementioned GUI--probably a zillion little background daemons (usually with systray icons) that only keep one particular piece of software up-to-date. If your database server asks you to install the Ask Toolbar you've got a problem (haha, Java how I despise thee).
* Lack of built-in pagination or LIMIT-like mechanism. Grabbing a limited subset of any given query in SQL server is like pulling teeth! Just look at this StackOverflow question/answer on how to do pagination with SQL server: http://stackoverflow.com/questions/109232/what-is-the-best-w... If you didn't find that answer by googling you'd be in hell trying to figure it out!
* If your software isn't built on top of Microsoft tools/frameworks working with MS SQL Server is a huge pain in the ass. You'll quickly get into dependency hell just trying to get the necessary modules/libraries working and you'll never get anywhere near as good performance as Microsoft's frameworks. Whenever I'm in this situation I feel like SQL server is a nail and if you're on Windows they give you a hammer but on any other platform they give you a screwdriver and say, "just hit it with the handle really hard. Oh, and use soft wood or plastic."
* Growing SQL server is expensive. Not usually my problem but it is always a concern. It's never as simple as "just adding more servers" because you not only have to pay for the SQL Server licensing you also have to pay for the Windows licensing and all the other licenses that are intrinsic to any Windows install in any given enterprise environment.
Sharepoint kind of sucks, but it sucks less than most proprietary corporate intranets. It's an out-of-the-box intranet server app and it's pretty good for small-medium enterprises. Beats Lotus Notes anyway.
From there they jump to the products you mention. Sharepoint is terrible for building websites, but recognizes and uses AD permissions out of the box. So does Office. So does Lync. Etc.
I bet MS makes and sells more hardware. XBox alone must outnumber all IBM hardware sales. (ThinkPad hasn't been IBM for several years now).
IBM's system hardware revenue for FY 2012 was $17.6B. (http://www.ibm.com/annualreport/2012/bin/assets/2012_ibm_ann... page 30). IBM also manufactures components and licenses hardware designs, such as the CPUs used in the PS3 and Xbox 360.
Microsoft is still not as big a hardware player even compared to an IBM that has sold off a good chunk of their hardware manufacturing.