The tablet Nexus device is expected to support "Jelly Bean", which is Android 4.1, and sport a 7-inch screen, quad-core Nvidia Tegra 3 processor, and 1GB memory.
The interesting part about these specs, is that at the price point and size, it will compete with the Kindle Fire. That said, it will be faster and will feature a true Android experience, not an Amazon-Android one.
James Kendrick brought up a good point around why Google may want to make its own tablet this time around. It seems that it has been struggling with its Android update process across OEMs and carriers, so maybe the company just wanted to handle this one on its own. We saw similar things happening with Microsoft over the years, where the flexibility of what amount of memory could go in a handset, the form factor, and even the processor speed could differ widely. This may also be why Microsoft is going it alone with its Surface device.
I wonder if the device will be announced on Wednesday or Thursday, and also if this will be the device that developers are given to start developing on straight away. It would be a great way for Google to force it into the channel, with new apps being created even during the conference.