"Apple Watch" instead of iWatch.
That's not really a change. Throughout the "i-Timeline", Apple has always offered non-i names. For example, the iPhone was announced at the same event as the Apple TV. My guess here is that iNames are expensive and a distracting hassle that brings with it huge risks since they could face a possible unreasonable settlement in any given country. iWatch faced a ton of legal attacks even without any official announcement from Apple about a watch.
Their desktop operating systems...
True, but they literally ran out of cat names. Also, the names weren't an indication of anything, they were just arbitrary names used to differentiate the versions along a given theme. They changed the theme; they didn't go from 10.6.1 to 11.
They chose to go with "Apple Pay" instead of of what some expected, "iPay".
Same legal issues and reasons as to why they went with Apple TV, Mail, Pages, Numbers, etc...
Also it's worth noting that for Apple Pay and Apple Watch, these were new product lines. It's not as if Apple went from iPhone to Apple Phone or iPad to Apple Pad. There was no naming convention to begin with for their watch or payment system.
There is a naming convention with the iPhone, and it's worth noting that unlike iNames, Apple owns the naming convention. There's no downside or risk to using it, unlike the costs and risks of using an iName. Apple doesn't need to worry about costs or risks of using the S for the second edition of the same body.
Now, I could see that Apple may offer a different body this year and skip the S, or even that Apple may decide that the body won't be changed for at least a couple more years so the S convention will be broken anyway, but the rumor isn't giving any indication of this. All the rumor is saying is that advances in the iPhone this year will be so great that is will go straight to 7. That's just BS clickbaiting hype. Copy and paste that every year along with "this year's iPhone is coming in the spring this year" followed by "due to component constraints/production delays, the iPhone is being postponed until the fall". FFS just put Apple Television posts on auto-publish and be done with it.