Bloomberg is reporting that Apple has begun production of the iPad 3 for an expected March 2012 release.
[iPad 3] will sport a high-definition screen, run a faster processor and work with next-generation wireless networks, according to three people familiar with the product. [..] The tablet will use a quad-core chip, an enhancement that lets users jump more quickly between applications, two of the people said.
The March date is spot on, and the 2042x1536 Retina display screen is an easy bet at this point. Apple could go quad-core with the A6 chipset as competing tablets have recently done, but Apple's integrated hardware/software approach has thus far let them do more with less.
LTE still feels like a wildcard to me. While Verizon has better deployment and AT&T is starting to ramp up, Sprint and T-Mobile are behind and international carriers are hit and miss (and just like 3G GSM, frequencies are not always compatible).
The Retina display and A6 alone will make for a compelling upgrade, but for those in LTE areas, it could make it a no brainer.