This story has been updated to reflect the most recent speculation.
Indications are Apple will hold an event on March 7 in San Francisco to introduce the iPad 3.
According to the Web site The Next Week, Apple is in "crunch mode" preparing for an upcoming event.
And if form holds, that means Apple's third generation tablet will go on sale there soon after, perhaps the week of March 12.
iPad 3's improvements over the iPad 2 are known only to the degree of certainty that anything about Apple's plans can be ascertained before an event. Having said that, four upgrades are pretty sure things, based on published speculation:
Higher-Resolution Retina Screen
iPad 2's screen resolution is currently 1024 x 768 pixels. It's a pretty sharp screen, yes, but look closely. You'll see some jagged edges on text and other objects, which makes smaller type harder to read.
Apple's Retina display technology, which enables iPhone's sharp graphics, could give iPad 3 a screen resolution of 2048 x 1536, double that of iPad 2 and the highest screen resolution of all tablets and many laptops.
Without the jaggies, smaller type will be easier to read without squinting, while videos and games will seem to nearly pop off the screen.
More Powerful Processor
iPad 3's brain will likely be the Apple designed A6 processor. Best speculation is the A6 will be either a dual- or quad-core, 1.5 or even 1.7 GHz engine, compared to the dual-core, 800 MHz processor in the iPhone 4S and iPad 2. In other words, the iPad 3 could be twice as powerful and twice as fast as iPad 2.
Aside from everything happening zippier, one likely benefit of the beefed-up A6 engine will be to bring Siri to the iPad.
UPDATE: It looks as if the iPad 3 will not use the A6 processor, but an updated version of the A5 chip found in the iPad 2, the A5X, a dual core processor with likely 1.x GHz capabilities.
Longer-Lasting Battery, 4G LTE
Surreptitious photos taken of a purported iPad 3 case indicate there's room for a battery that looks to be around 20 percent larger than the battery in the iPad 2.
iPad 2 can run around 10 hours on a single charge. Given the larger battery plus more powerful but more power efficient processor and other power savings Apple always seems to find, iPad 3 may last as long as 13 hours.
Also on the high-probability list: iPad 3 may be the first Apple device able to operate on AT&T's, Verizon's and maybe Sprint's 4G LTE networks, as well as current 3G networks.
Lighter and Thinner
Reportedly, iPad 3's bigger battery is also paradoxically lighter and thinner than iPad 2's battery (many lithium-ion cells have gotten larger yet lighter in the last year).
In addition, the A6 processor also is a few microns thinner than the A5, which all could result in iPad 3 being a hair thinner and slightly lighter than iPad 2.
My guess: iPad 3 will maintain at least the same form factor so iPad 2 accessories – particularly the Apple Smart Covers – will still fit.
What about Siri?
I don't think it's technology keeping Siri off the iPad, I think it's all about maintaining a satisfactory user experience.
Siri relies on having a connection to the Internet to answer questions. iPhone 4S maintains this constant connection via 3G, so Siri is always at the ready.
But a Wi-Fi-only iPad wouldn't keep a constant internet connection. We're likely to try and use Siri when the iPad isn't connected to the net, and then be frustrated when she doesn't answer. So if Siri becomes available for iPad, Apple may decide to include her only in models that include a cellular connection.
UPDATE: Speculation is that SIri will be integrated in the new iPad 3, but it's unknown if it will work with just a Wi-Fi connection. iPad 3 also likely will include 1080p HD video recording.
One more thing…
Based on past history, odds are high that Apple will add something unexpected (although now that we're speculating about these capabilities, perhaps not so unexpected). In order of their likelihood:
You may be able to sync iPad 3 wirelessly – just plug your iPad into AC power within a Wi-Fi proximity to your PC and the two will sync, which you can already do with iPhone 4S. No more will you have to jack it directly to a PC to transfer files.
I've also read speculation about iPad 3 being able to be charged remotely – that is, charge its battery without being directly wired to an AC source.
We'll soon find out. Stay tuned.