AT&T's handset plans for 2009 have been laid bare through a set of leaked slides revealed by Engadget, and include an Android slider as well as a second-generation Palm device.

The Android handset is from HTC, but doesn't appear on the previously-leaked line up. Branded the HTC Lancaster, it's aimed at social networking and features a sideways-sliding keyboard. From Palm comes the Palm Eos (Castle), a successor to the Centro that might, or might not, be a WebOS device to follow the (hoped for) success of the Pre.

The slide pack also has details of new Blackberry devices that AT&T will be ranging before the end of the year, including a new Pearl supporting 3G and the Onyx, which boasts a 480x360 resolution screen.

HTC's Lancaster sports the same reduced chin as the Magic, but slides sideways to reveal a QWERTY keyboard. According to the slide, it's scheduled to launch in August, though a footnote states that "AT&T standard UI has been requested, which puts the schedule in question". The Lancaster also features a "Unique HTC Social Messaging User Interface", which is interesting both in terms of HTC using software to differentiate its offering and the increasing integration of social networking services into mobile telephone interfaces.

The Palm Eos has already been leaked as the next WebOS device, though the slide makes no specific reference to the new operating system, other than noting it offers a "New Palm OS experience". A cut-down device to follow the Pre makes sense, and there's nothing in the specification that precludes WebOS being the platform, so it's hard to imagine it won't be. Palm will need to sell a lot of Pres if it's going to be able to afford to support a range of WebOS devices, however.

Overall, it looks alike quite a line up from AT&T, and makes one wonder why the company is so desperate to extend its exclusive access to the iPhone - unless Apple has something really remarkable to announce next week. ®