I hope this ends well. I really, really do.

CNET was the first to report on AT&T’s massive plans to make Nokia’s Lumia 900 its new hero device when the Windows Phone 7 smartphone goes on sale this week. There’s no denying the 900 is an interesting phone, priced at just $99 on contract and stocked to the gills with cutting-edge features including 4G LTE support, a 4.3-inch Super AMOLED display, and a polycarbonate body available in striking colors like Cyan. And a few months ago at CES I sang the device’s praises to all who’d listen, citing the beautifully fresh Metro design language and Nokia’s penchant for building stellar hardware. But is it worthy of superstar status right out of the gate? And more importantly, in a marketplace dominated by Android and iOS, is it a smart bet for AT&T to lay so much at the feet of Windows Phone?

“Before you walk in to the store, you know this is our hero phone,” Jeff Bradley, SVP of devices at the carrier, told CNET’s Roger Cheng last week.

That’s a huge bet to make given how little traction Microsoft’s mobile platform has gained in the US since the first American WP7 devices were announced in late 2010. As Todd reported, the latest Nielsen data shows WP7 holding a four percent share of the American smartphone market. Android and iOS combine for a whopping 91 percent cut of the pie, leaving Blackberry five percent. On the one hand, that means AT&T likely has little to lose in pushing Windows Phone hard: So many of their customers and potential customers are already so well aware of Apple and Google’s offerings, why not put some muscle behind the new upstart? The worst thing that could happen is a customer walks into an AT&T store bent on buying an iPhone or Droid, gets a big sales pitch about Lumia 900, and goes home with an iPhone or Droid anyway. Nothing lost in the process, and maybe Lumia/WP7 is filed away in said customer’s mind for the future.

If AT&T doesn’t hype Nokia’s new flagship, people will never know there’s an alternative to the iPhone/Android duopoly, right?

But then there’s the other worst case scenario to consider. The one in which Nokia’s utterly disastrous track record of selling smartphones in the U.S. proves prophetic. The one in which people go to the store to buy an iPhone, get bombarded by salespeople pushing some other phone too hard, and one-eighty their ways out of AT&T and over to the Sprint or Verizon outlet at the other end of the mall. The one in which so many of your friends have told you how awesome their iPhones and Galaxy S II’s are that why in the world would you possibly want a big fat blue phone that can’t even run Instagram? The one in which it’s too late for even money-laden Microsoft to gain mindshare in the mobile market.

Nokia Lumia 900 in white

Everything we know right now tells us that Microsoft and Nokia are footing the bill for the hero’s welcome AT&T is throwing for Lumia 900. So it’s easy to say that it’s not costing the carrier anything to take a chance on building a new brand around a third major mobile platform. But there is a cost. There’s the risk of turning off customers by pushing something they don’t want. There’s the risk of turning off HTC and Samsung and the other OEMs by pushing Nokia – Nokia, the longtime black sheep of the U.S. smartphone market – so hard at the cost of selling your longtime partner’s goods. And then there’s the risk of alienating Apple and Google.

AT&T needs Apple far more than the other way around right now. And honestly, who knows what Google might do next. Maybe they go nuclear on Amazon. Maybe they go all-in on Google Voice as a “minutes-free” alternative to traditional cellular service. Or maybe they see fit that AT&T never, ever gets a top tier Android device again. Do I think that’ll happen? Not likely. Then again, I never thought Google would buy Motorola, either.

Nokia’s Lumia 900 looks to be an excellent smartphone, and a worthy icon of Microsoft and Nokia’s big mobile comeback play. I still think Windows Phone 7 is a beautiful operating system, even if my personal love affair with the platform has waned in the cold light of relatively slow developer support and Bizarro World annoyances like, “Skype is STILL only in Beta. And oh yeah, it can’t run in the background.” You may hate FaceTime, but I video chat with people all the damn time. Yes, from my phone.

For every “Noah and his weird video chat thing,” there are millions of other smartphone customers out their with millions of their own use cases and quirky preferences. Android and iOS have grown tremendously in the past five years (give or take) and while each has its problems, each is also able to meet a wide variety of customer needs in different ways. Windows Phone 7, not so much, at least not yet. The platform needs exactly what AT&T is giving it in the form of making Lumia 900 its new hero device: A giant kick in the mindshare-wearing pants. Frankly, a huge launch on a huge carrier backed by huge media is the only shot Microsoft, Nokia and WP7 have got. It’s a big risk for everyone involved, but it’s the risk they have to take if they want to keep playing the game.

In the name of competition and innovation, I hope it works out well. I really, really do.