Largely based on Nokia’s strong support, Windows Phone is set to regain the No. 2 rank in the smartphone operating system in 2015. Finnish-based Nokia in 2009 lost its second-place worldwide ranking because of rising competition from Google Inc.’s Android and Apple Inc.’s iOS.

In 2015, however, Windows Phone will account for 16.7 percent of the smartphones shipped, up from less than 2 percent in 2011, according to the IHS iSuppli Mobile & Wireless Communications Service at information and analysis provider IHS (NYSE: IHS). This will allow Windows Phone to slightly surpass Apple’s iOS to retake the market’s second rank behind Android, as presented in the table below.

That’s awfully confident-sounding. Windows Phone is “set” to become #2 by 2015 and “will” have market share of 16.7 percent and “will” overtake iOS. And hey, it’s an analyst who knows his stuff doing the talking, so the rest of us should pay attention.

But as Todd Bishop of GeekWire points out, iSuppli also released smartphone projections in 2009. Back then, it thought that the operating system then known as Windows Mobile would hit the #2 position by 2013, not 2015. And the #1 operating system in 2013? Why, that was, um, set to be Symbian. An operating system which is already so moribund in early 2012 that iSuppli no longer bothers to break it out into its own line.

A reasonable and well-informed person might express opinions about the long-term prospects for various mobile operating systems. Expecting Nokia’s commitment to Windows Phone to result in a substantial spike in sales isn’t the least bit nutty. But making market-share forecasts for 2015–down to the decimal point!–and discussing them as if they were factual is goofy at best and disingenuous at worst.

The only prediction I feel safe making about smartphones in 2015 is that it will be startling if nothing disruptive has happened in the category by then…and once a category gets disrupted, all bets are off. (Strangely enough, this 2006 story about phone market share in 2010 doesn’t mention the iPhone or Android.)

Really, making forecasts about mobile devices for 2015 is a little like predicting the results of the 2016 New Hampshire presidential primary today. And nobody is silly enough to do that.

I wrote about all this last year when IDC released its 2015 forecast, which also had Windows Phone shooting up to the #2 slot. I came back to the topic when Gartner published a tablet forecast. (Since Gartner’s numbers came out, HP canceled its WebOS hardware and Intel discontinued development of Meego, rendering the Gartner forecast for 2015 obsolete four years ahead of time.) I’ll probably write about it again.

Here’s a smartphone-related something I’d like to see happen by 2015: Wouldn’t the quality of discussion about the mobile market improve meaningfully if research companies stopped making these forecasts–or at least if the rest of us stopped taking them seriously?

Researcher Kevin Keller told BusinessWeek that Apple has seemed to generally spend about $170 to $180 to produce iPhones, from the original model in 2007 to today’s iPhone 4.

The iPhone 3Gs initially cost about $179 to produce, although that price has since dropped to about $134. That means Apple likely now only breaks even or makes a very small profit as it sells for $99 from AT&T.

Inside, iSuppli found that the device uses a similar A4 chip that is also seen in the iPad, and confirmed the antenna is in the metal strip around the phone. As you’ve seen here on Technologizer, that’s been a potential problem for Apple, although iSuppli makes no reference of it in its report.

There’s another outbreak of such stories today. But this one was prompted by a new report from iSuppli that’s pretty darn definitive: It says that global unit sales of notebooks surpassed desktops for the first time in Q3 2008. Unless you want to wait for the day when there are more laptops on the planet than desktops, this is it–laptops have overtaken desktops. Period. Finally. End of need for future Groundhog Day stories on the matter.

So can I make a modest proposal? If the majority of personal computers being sold everywhere on earth are laptops, they’re not the variant of the PC they were when they first popped up in the 1980s–they are the PC. It’s desktop computers that require qualification, and the time will come when desktops become an endangered species, just like minicomputers were by the 1990s. Which means that it would be perfectly reasonable to redefine the unmodified term PC as meaning a computer that’s portable.

I’m not promising I’ll stick to such a policy here–if I’m the only person who does, I’ll just confuse people–but I kind of like the idea.