Although the firm has yet to issue an official announcement about either product, Microsoft's Surface lineup is about to get a bit bigger with two long-anticipated additions. An LTE-equipped Surface 2 tablet has popped up in AT&T Wireless and Microsoft Store locations, and a Power Cover that improves battery life of most Surface tablets will ship next week.

The Power Cover is perhaps the more eagerly awaited of the two. Microsoft announced the Power Cover at its September 2013 Surface 2 launch event, noting that the combination keyboard cover and battery would ship in early 2014. I wrote about this intriguing accessory at the time in "Surface 2 Accessories: First Impressions and Photos" and "Surface 2 Accessories - Visually."

I also spent a bit of time with the Power Cover at the launch event, and it's pretty much what you'd expect: A slightly thicker and heavier Type Cover (sans keyboard backlighting) that provides, Microsoft says, about 70 percent more battery life. It works with the Surface 2, Surface Pro, and Surface Pro 2 (not the original Surface RT), but it's particularly desirable for owners of the original Surface Pro, which offers lackluster battery life.

The Power Cover will retail for $200. You can preorder this accessory now from the Microsoft Store. I'll be reviewing the Power Cover later this month.

As for the LTE-equipped Surface 2, Microsoft's Panos Panay revealed the existence of this device in a Reddit live chat in the wake of the Surface 2 launch event. As with the Power Cover, he said the Surface 2 LTE model would ship in early 2014.

Microsoft has been silent about this product since then. When I asked about it in late January, I was told that the Surface team had nothing further to add about the expected delivery date. Now, the release is apparently imminent. Enthusiast blog Windows Phone Central reported this week that the device, called Surface 2 64GB Tablet (AT&T 4G LTE), will be priced at $679—a $130 premium over the normally aspirated Surface 2 64GB version. As its name suggests, the device will work with AT&T's network.

It's not clear whether versions for other wireless carriers will be made available or whether an LTE-equipped Surface Pro 2 is on the way, as well. The LTE version of the Surface 2 will be sold through Microsoft Store and AT&T Wireless, WPCentral says. The device is expected to be visually identical to the other Surface 2 models.

Of course, the biggest Surface update is still a mystery. After planning to deliver a Qualcomm-based Surface mini last year alongside Surface 2 and Surface Pro 2, Microsoft at the last minute pulled the product. It's not clear why, but all of Microsoft's hardware makers have opted to use Intel-based chipsets, not ARM, in their own Windows mini tablets, and it's possible that the firm is changing the design accordingly. I've not heard anything new about Surface mini in months.