I meant "confirm" as in "strengthen the suspicion". It's one of its definitions, even if not the most common one. Feel free to look it up.
It is a known fact (or well, highly guessable at least), that Microsoft's goal has shifted from selling Operating Systems, to having a mostly free platform ("free" in this case implies the user has paid the "Microsoft Tax" at least once in the life of the device), as a means to make the Windows Store as accessible as possible.
All of the new features in Visual Studio 2015 regarding porting apps from Android/iOS, all the rumors that there may be Windows 10 phones "soon", etc. simply confirm this. Microsoft's goal is to make it as easy as possible to purchase things from the Store, so that they can get their cut of the sales.
I decided to install the Insider Preview on my laptop, as a means to evaluate Windows 10 before the final version touches my desktop, and so far I'm liking it. It does have a couple of annoyances, but overall it's good, and the in-place upgrade was flawless for me.
That said, to the point: I have a handful of updates in my WU that I decided not to install just yet. All of them popped up around the same time, and all of them are related to the upgrade process between Windows 7 and Windows 10. Once I decide to upgrade to Windows 10, I will unblock KB3035583 and friends, and let Microsoft upgrade to the new OS in-place.
I'd say that the fire element represents energy. Heat is the most obvious form of energy so it makes sense to use it as a representation of all energy interactions.
The other 3 elements represent the primary states of matter. Plasma wasn't discovered until much later, so it wasn't included in the list of elements at the time. Although, it could be said that the aether is dark matter, which would bring the total to 6?