The Sony Tablet S has been one of the tablets with a unique and interesting design in the market. While a lot of people were trying to replicate the slab form factor for their tablets, Sony tried to think about how to make a 9″ tablet that is easy to hold with one hand. Going by the initial reviews, they seem to have succeeded more or less, with reviewers declaring that it feels lighter than it is really is when holding it. Many claim it feels more like a 7″ tablet.
The 10″ tablets are usually hard to hold with one hand, because of the (still) fairly bulky weight (600+ grams, ideal weight for one-handed use is around half of that), and it's one of the reasons why people prefer 7″ tablets like the Nexus 7. It's just that some might find the screen size too small, which is why it's important to come up with innovations. Sony, in response, has tried to improve the usability of a 9″-10″ tablet.
Unfortunately, the Sony Tablet S arrived too late in the market, with an old version of Honeycomb, with Tegra 2, and at a fairly high price ($600). This ended its life cycle almost immediately. But it seems Sony may be willing to give it another try soon, with the second generation of the Sony Tablet S, that will launch almost exactly a year after the original. The tablet's successor, with the model number SGPT1211 has just won FCC approval, which means it won't be long before we see it in the market.
We don't know much else about it right now, but we can speculate about what it will have. First off, the tablet might benefit from the recent unification of their mobile divisions. This means that if they release this tablet, it will be a big project for them that they will take seriously. It should also be Playstation Certified, so you'll be able to play all the older PSX games on it, alongside all the native Android ones.
This means that it should have a powerful CPU and GPU as well, but it's hard to estimate what they will use. It could either be a Tegra 3, or if they release it later, a quad core Snapdragon S4 Pro, with an Adreno 320 GPU. I would still bet on Tegra 3, though. They may want to take advantage of the Tegra Zone as well, if they want to promote this as a gaming device.
The OS is most likely going to be Android 4.0, although they should really try to release it with Android 4.1 if they want the reviewers and potential buyers to be more excited about it. If they are smart, that's exactly what they will do.