Sony is working on not one, but multiple tablets for launch in 2011 to take on the bevy of devices already announced, launched, or available.

According to “a pair of highly trusted and proven sources” Engadget claims that “Sony is also working on two rather unconventional tablet form factors including a dual-screen Honeycomb clamshell and newfangled Windows 7 tablet slider.” 

The site says that the Android powered clamshell will sport a pair of 5.5-inch displays similar to the Kryocera Echo or Nintendo DSi. However, the "S2"  as it is known internally, won’t look like a square block, but an “oval cylinder when closed”.

Spec-wise the site is saying that it has been told that it will be very similar in performance to the S1 with a Tegra 2 SoC and WiFi + 3G radio on the inside and front- and rear-facing cameras on the outside.

However before you get too excited, the device might not even make it to market with “One source claims that the gap between the displays should be made smaller noting that the whole project is being met with skepticism within Sony. Another source calls the S2 an outright ‘dog.’”

The site says that “Sony's plan is to ship the WiFi + 3G equipped S2 to the US, Europe, and Japan before the holidays with a $699 targeted asking price.”

As for the slider?

It will be a VAIO-branded 9.4-inch Windows 7 slider similar to Samsung's Sliding PC 7 Series and the ASUS Eee Pad Slider due in October.