The Chronicwire (@chronic) has just pointed out that the iPad 3 will have 1GB of RAM.
It's been in plain sight since the beginning of February when BGR posted their exclusive photos of debug output from an iPad 3 development unit.
The (full) last line in the screenshot below says:
vm_page_bootstrap: 244276 free pages and 8396 wired pages
With some simple math:
244,276 (pages) x 4,000 bytes (size of a page) = 977,104,000 bytes = 977MB
The BGR shot Chronic is referring to was reported on last month. The information was apparently in front of us the whole time.