Microsoft is not the first company to do that. There's a longer trend ongoing, where vendors will have first convinced us to ue the cloud for interconnecting everything, and then let us pay for that service.
Sooner or later Google will do the same and will inform us that they'll reduce the free space, to convince us to rent for it. Google has already converted many services to a subscription form, or reduced the content available with the free offers. Youtube survives but is now severaly restricted (except for some large content producers). Don't forget that Google want to sell Google TV. Google has already reduced the maximum length of a video, and will soon limit the storage capacity per user for hosting their own videos (even if they are shared), unless these videos are enough attractive to get a minimum trafic from enough users (or from users of special interest for Google) that Google can use to promote other sold products: look at the usage conditions of Youtube: you authorize Google to reuse your content without limitation, including for promoting paid offers.
Apple does the same in its content stores. Facebook does the same, Microsoft does the same.
Look at Windows: it is not longer a strategic sale by itself, it is a "free" product used as a vector to promote paid offers sold by Microsoft. The MS cloud is the new strategy, including for Office. Microsoft now targets any OS, and provides solutions even for Linux users. I can already predict that very soon there will be a Linux distribution by Microsoft (where all solutions to connect to its sold cloud will be integrated). Microsoft accepts the presence of other browsers and will make sure that they can support without effort its cloud services. Microsoft welcomes also Facebook, Twitter, Android, iOS, OSX. Different platforms for different segments of markets (from end users to large server admins), but all good candidates to become customers of MS cloud solutions.
Microsoft has integrated now what made the success of Apple, Google and Facebook, and even Linux in servers, it will not fight directly against them directly, but will want to sell the best integration experience on all screens, all devices. For that MS will provide compatible solutions. He will stop soon selling device-centric/host-centric solutions, but will focus on solutions centralized to the single user account, connected from everywhere, on any network, on any device and OS. Even the "opensource" movement is no longer an enemy to figty against: in fact it is now welcome to help filling the remaining niche markets where other proprietary solutions would become too costly to maintain alone.
The OS is relagated progressively to the same background support as the hardware. What Microsoft wants is to sell personalized services, focused on personal experience, or on precisely targeted enterprise environments (working with their internal structure and hierarchy of powers and delegations of roles).
May be later Microsoft will start targeting other markets, notably the bank market (the success of Paypal may cause Microsoft later to buy some bank and sell its own credits, just like what car manufacturers have done to survive). Microsoft wants to be central in everything that means payment, business, shopping. Software becoming more a service (that will be subscribed with monthly billings, just like internet and mobile phone subscriptions).
And isn't it what Google, Amazon, and Apple are also doing? Just like old telcos that are now large ISPs doing also the same thing ?
There's already Microsoft store, Microsoft music, Microsoft cinema, Microsoft travel maps, Microsoft education, Microsoft security. May be there will be Microsoft hotels and travels, Microsoft cars, Microsoft food, Microsoft health... When will there be a Microsoft religion service, Microsoft police, Microsoft justice, Microsoft currency, Microsoft casino and sport betting ? Transpose everything above to Google, Amazon, Apple and Samsung.
Note that we already have now Microsoft laws, Google laws (now more powerful internationaly than national laws). Microsoft and Google monthly billings will also become the Microsoft and Google tax: pay, work for us, or go to jail without rights (and you won't be allowed to vote even in your local democracy if you have not "connected" your life to one of them, you'll become a dangerous "suspect" under massive surveillance, and later a target for hunts)... China is already doing this in several parts of the world (southern Asia, Africa, it starts doing it also in Europe). Korea/Samsung/LG has the same strategy.
Ony USA attempts to do something (but on the miliitary and federal laws system)... but very inefficiently and without so much success. Private US companies are instead providing (and services) to the US government.
Look at what is happening also in China where the integration of all services in a giant company is also going fast (but in a very large controled market, from which large and corrupting Chinese companies are invading the rest of the world in lots of domains, including agriculture, lands and real estates, banks, luxury products, gambling, travels and hotels, in order to apply the Chinese political rule on the rest of the world).