At some point you have to decide whether the the perfect (everyone using Windows phones/tablets and MS Software) is the enemy of the good (a lot of people using MS Software).
Microsoft has for whatever reason never hit the target with mobile platforms. I guess the Windows Phone is decent enough by some accounts but was just way too late to the party.
So they can try to make money selling mobile software for a mobile platform that nobody uses, or they can just accept reality and sell the software on all platforms.
It's that or gradually become more and more irrelevant to a very large segment of the computing market. I think there more to this than just 'accepting their fate' to never be a successful mobile devices company.
If their mobile software succeeds and becomes as near-essential as Office once was, that could well create a halo effect for their mobile platforms. After all if you use MS software every day on your phone or tablet, why not buy an MS phone or tablet next time you're in the market for one?
Their first order of business in mobile is to become relevant again. Today took their best shot at that in a very long time.
In the console game world, softwares(games) can decide the fate of consoles. Dreamcast failed BEFORE PS2 is released, due to Final Fantasy X, XI and XII. Another example is that Xbox survived because of Halo.
In my opnion, Office is the ace software of Microsoft. It is even the de-facto standard. Therefore Microsoft should keep them exclusive on their platform.
Keeping Office off the iPad until now hasn't prevented millions of customers from buying them, or pushed any significant number of users to Windows 8 (RT) tablets instead. Microsoft's indispensable programs haven't been sorely missed for the last four years.
Super Mario 3D World is 1080p (I took your 'REALLY HD' to mean you didn't realize Mario was already in HD), it's also the best co-op multi-player experience I've ever had:
So, are they going to discard Windows (|phone|tablet|...) platform and become a pure third-party? It reminds me of Sega.