Curious timing: Goldman Sachs issues another report saying the iPad and tablets are hammering Microsoft, then anonymous sources tell the New York Times that Windows 7 tablets are part of Steve Ballmer's CES keynote.

The Times piece says Ballmer will show Dell and Samsung tablets running Windows 7 and may even give a peek at a device running Windows 8.

A Microsoft spokesman declined to comment, saying "we are not talking at all about CES."

Ballmer already said these devices are coming. He told analysts in July that Microsoft's big push into tablets will come in early 2011 with the release of new Intel hardware for mobile devices.

One of the analysts he was talking to was Goldman's Sarah Friar, who is unlikely to be convinced by a whispery blog entry saying "wait until January!"

Still unanswered are key questions about the next generation of Windows tablets: When exactly will they go on sale, and how much will they cost?

If they're $1,000, they'll die the same quick death as Microsoft's ultra-mobile PC concept, which debuted on Samsung hardware in 2006. The device Ballmer will show in January is "similar in size and shape to the Apple iPad, although it is not as thin," according to "people familiar with the device" who spoke to the NYT.

An appearance at CES doesn't mean the devices will go on sale in January. The show is really for retailers to see products that they'll carry later in 2011.

Hewlett-Packard, for instance, waited until late October to finally, and quietly, take orders for the Win7 Slate PC that Ballmer showed last January. HP was a special case, though, as it's trying to build consumer tablets on its own operating system now.

I'm curious to see whether the "Windows 7" operating system on the tablets will be the full-blown version or stripped-down versions designed for consumer-electronics and portable devices.