We've already heard rumors that there will be another Nexus 10 later this year (codename P600), arriving with Android Key Lime Pie, and recently we also learned that Samsung may make a 12.2" tablet (codename P900).
The 12.2" one will supposedly be a "Note" tablet, and will come an with S-pen. It will also have an Exynos 5420 chip with a Mali T628 GPU, that's rumored to be faster than the Snapdragon 800, and will probably come with a bigger battery, too, inside that 12.2" device. The tablet will also have a high 2560x1600 resolution screen, just like Nexus 10 last year.
Since this will be a Note tablet, I expect it to arrive with Android 4.3 and Nature UX on board, even if it launches at the same time or soon after the new Nexus 10 is announced. But even so, I've been waiting for a proper Note tablet with a high resolution and a very powerful chip inside, that helps it work very well, especially for drawing and such.
The 10" tablet codenamed P600 is most likely the new Nexus 10, which will also have a 2560x1600 resolution, but this one will use the Snapdragon 800 processor, and the Adreno 330 GPU (about 2x faster than Adreno 320). Presumably this one will use a smaller battery, so it will need a more efficient processor. Plus, it should come with Android 5.0, and Google already has most of the driver written since the Nexus 4 and the new Nexus 7, which used a similar Krait architecture. Using Krait again will make it easier for Google to optimize KLP for these devices.
We don't know anything about prices yet, but I'd expect the new Nexus 10 to cost about $400 again. The Note 12.2's price on the other hand should be a little more unpredictable. It will have the S-pen and the active digitizer, which should cost an extra $100 or so. So it's possible Samsung will make it cost $500, for the 16 GB model. This means it will have specs similar to the upcoming iPad, but with the extra S-pen added to it, while costing the same. So it wouldn't be a bad price at all. However, I have no doubt that they could squeeze 32 GB in there for the same price, and still be able to make a profit. That would be a more ideal value/buck, but I'm not convinced Samsung will do that.
I have a feeling both tablets will be great, and the new Note tablet could be easily recommended to people who like to draw, while the new Nexus 10 with the brand new KLP could be recommended to everyone else who wants a larger tablet than the new Nexus 7.