According to sources who have been reliable in the past, Apple currently plans to hold their iPad 3 announcement on Wednesday, March 7, 2012. Along with the 2048x1536 Retina display, the iPad 3 will feature a quad-core Apple A6 system-on-a-chip, and possibly 4G LTE networking.
The March 7 date fits with what AllThingsD reported last week, about the next iPad event being scheduled for the first week of March, and Wednesday is a traditional day for Apple to hold these types of events.
Whether Apple would simply improve and optimize the current dual-core ARM Cortex A9 processor found in the Apple A5 SoC, or go quad-core has been a lingering question, with 9to5Mac finding code references to quad-core but The Verge hearing otherwise. However, it sounds like they're going quad-core.
4G LTE networking has been another mystery surrounding the iPad 3, with a compatible Qualcomm chipset becoming available, but international LTE coverage is still slim, and in some cases a year or more away. It sounds like Apple has 4G LTE lined up for iPhone 5 this October, but we're still not certain if the iPad 3 will get it earlier. Verizon is going to want iOS devices that go faster than 2-3mbps, of course, especially with AT&T offering HSPA 14.4, and potentially faster, models. Apple could release a 4G LTE variant model, targeted at Verizon, AT&T, Rogers, Bell, and other carriers that have rolled out enough support to see demand, or they could wait and debut it in the next iPhone instead. (No doubt Apple has already decided, it just isn't clear to us which way they went for the iPad 3.)
Other rumors from iLounge have included better cameras, either a 5 or 8 megapixel rear camera and a FaceTime HD front camera. We haven't received any information on these, though any camera Apple includes will have to fit into the thin iPad 3 casing. Likewise, they're probably going to want to keep component costs down low enough to maintain their $499 entry level price tag. (Even if Apple decides to keep iPad 2 around, with a low end, low storage offering at $399.)
Again, these are rumors, and an extract of a lot of information we're still trying to properly sort, but we'll update when and as needed to clarify and correct. Either way, we'll only know for certain when Apple executives take the stage next month to officially announce the iPad 3.