Will iPad transition from product to product line?

We've been arguing for while now here at TiPb about whether Apple will leave the iPad as a singular product, the way iPhone and iPod touch are, or transition it to a product line, the way MacBooks are?

So far Apple has resisted even leaving last year's model available as a cheaper 8GB entry-level model, the way they've done with the iPhone since iPhone 3G and experimented with one year with the iPod touch 2.

There were rumors earlier this year that Apple might push up the release iPad 3 (or iPad 2 Pro) to this fall, resulting in two iPads being available -- the still current iPad 2 and the more expensive, Retina Display version. According to TiPb's sources, however, has since moved iPad 3 back to the traditional spring release schedule, perhaps because those Retina Displays can't yet be produced cheaply or consistently enough to meet Apple's demand.

When iPad 3 is released next year, will Apple take the opportunity to leave iPad 2 on the market, perhaps at a cheaper $399 for 8GB price point? That's a small step towards making a product into a product line.

The bigger leap would be multiple screen sizes. 7 inch tablets have been released by Samsung and BlackBerry, was going to be released by HP webOS, and rumor has it will soon be released by Amazon. None other than Steve Jobs has said Apple doesn't like the 7 inch size, that it's not a great experience, that it required people to shave down their fingers. But he also said people didn't want to watch video on their iPods and we all know how that turned out...

What about a bigger screen size? Samsung already makes pretty much every sized tablet from 5 to 11 inches -- in 1/2 inch increments! -- but much larger tablets still haven't really been tested. If rumors of Apple stretching the Retina Display on iPhone 5 to 3.7 or 4 inches turn out to be true, could they try to stretch the rumored Retina Display on an iPad 3 (or iPad 3 Pro) to 12 inches? I know, speculation based on rumors stacked that high is the blogging equivalent of playing Jenga on top of unicorns riding on rainbows, but...

That's about the only other factor I can see Apple exploring. They don't even disclose processor or RAM details, so a product line based on those things don't really make any sense -- you'll never shop for an iPad the way you shop for a Dell. Part of Apple's strength and success has always been its crystal clear product lines. Right now there's one iPad and all you have to choose is front color, storage size and Wi-Fi or 3G.

Next year, could it be budget iPad 2 8GB or iPad 3 (by color, size, and radio), or could it be more? 7 inches for highly mobile readers, 9.7 inches for general purpose multitaskers, and 12 inches for professionals who push pixels or productivity? Next year, could the iPad go from product to product line? If the iPad is increasingly becoming the future of mainstream computing, will it have to?