I think iPad 3 will be like this.*
1. Retina display 2048x1536
2. Siri
3. A6
4. Same 10-hours battery
5. Same price
6. Combine GSM&CDMA
I think iPad 3 will be like this:
1. Higher resolution display, presumably 2048*1536 pixels
2. A6 processor:
...- Either a quad core 1 GHz processor or a dual core processor clocked between 1 GHz and 2 GHz
...- 1 GB of RAM
...- Improved graphical power
...- Perhaps a fifth (or third) core for low-power actions (like in Asus Eee Pad Transformer Prime) [smaller chance]
3. $100 price cut, 16 GB model dropped, 32 GB: $499, 64 GB: $599, new 128 GB: $699
4. Improved front facing camera, FaceTime HD
5. Improved back facing camera (otherwise pictures will be very pixelated when looking at the high resolution display)
6. Bluetooth 4.0
7. GLONASS support in cellular network model
8. Only one cellular network model supporting both GSM and CDMA
9 Similar or better battery life
Now, all the things named above will certainly be added to the third generation iPad. However, there are also some smaller things of which I am not certain at this moment:
1. LTE support
2. Small design changes
3. Camera flash (seems unlikely, but hey, you never know...)
Hopefully, Apple will also add a feature no one is really expecting.