I could definitely see this future product line-up at Apple, would be pretty applicable to todays products:
- iPhone Mini (4") - The smallest device in the line-up, for the one-handed users.
- iPhone Air (4.7") - The thinnest device in the line-up, 6.9mm, hence "Air" moniker.
- iPhone Plus (5.5") - The largest device, with a few extra features, tiny bit thicker at 7.1mm.
- iPad Mini (7.9") - Smallest
- iPad Air (9.7") - Thinnest (think iPad Air 2 vs current Mini)
- iPad Plus (12.2") - Largest
The iPhone Mini would be an iPhone 5S repackaged into the iPhone 6 case, with a 4" display. Scrap all the old products, such as the iPhone 5S, 5C, iPad Mini 1, Mini 2, Mini 3, Air 1, et c.
While I must say that I very much like the option of buying the iPad Mini 2 for a great price, rather than only having the Mini 3 as an option, this does cause a very odd product line and I don't think it's right for the long run. You don't see Apple selling 2011 MacBooks along their 2014 models (don't ruin my argument by bringing up the cMBP from 2012...) neither do I think they should sell a 2011 iPad Mini in 2014.