Nokia has announced the Lumia 810 and obviously from the name of the device, we can deduce it is not exactly the same as the Lumia 820 but a variant of it.
So let's take a look at the major differences between the 2 devices.
These are the only differences between the 810 and 820.
The 820 is 15grams heavier (likely due to its thicker shell).
The 810 however is longer and wider than the 820, which doesn't explain why the 820 is heavier!
The 810 does have a better battery life than the 820, boasting of 10.2hr talk-time, while the 820 is just 7.5hr talk-time
Apart from these, eveything else is absolutely the same, both have 4.3 display, 1GB internal memory, WiFi support, wireless charging capabilities, 8MP Carl Zeiss camera, ClearBlack Display screen, 30fps video recording.
They will both be available in 7 colors (Red, yellow, Black, White, Grey, Purple and Cyan).
You can see the comparison in full details on Nokia's Comparison page