I have a 2007 iMac AL - first of the Aluminum era. Let. That. Sink. In...
While the form factor of iMacs has been refined, the overall 'look' of the iMac has been the same for over a decade — until the iMac Pro debuted with black. Even so, not much changed, visually. A brand new iMac comes with a color scheme and overall look that is 11 years old - more than half the lifespan of the entire iMac line itself. It's time for some bold moves...
I think Apple should split the iMac line in two: iMac Express and the mid-range iMac (keeping iMac Pro where it is).
The iMac Express would return to a smaller footprint with sharp-looking polycarb enclosures (perhaps with some sort of translucent LED lighting tech so that you could delicately and evenly make your iMac most any fruit flavor you want). The original iMac case had some lovely sub-dermal textures to it, and it would be cool to recapture some sense of that depth and elegance. Reduce the screen configs to 18" and 22" widescreens and maybe even run off an A chip instead of Intel. Include an HDD and, instead of an SSD option, maybe a 'backpack' SSD notch so an external SSD could connect via USB3 and fit conveniently somewhere on the back, out of site, without afflicting the overall design (unlike, say, that white plastic dongle hanging off my $2,500 MacBook Pro). If they price pointed the base model below $1,000, it would be a hot, trendy machine that would attract new customers and those looking for a simpler, practical desktop. The lifecycle would be 3-4 years.
For mid-range iMac I propose they maintain the gist of the current form factor but with some fresh color concepts and, maybe, extra camera(s) and/or sensor(s) for VR. Here again, I'm more intrigued by great looks rather than materials used: If they crafted these out of a, say, a newer composite material that looked great, is light, environmentally friendly, supports the machine itself (eg. thermal regulation, noise, etc.) AND enhances upgradability (RAM, SSDs, graphics cards, SD slot), I'd be far more interested and excited! Watching Steve's keynote where the iMac was introduced reminded me of an Apple that also announced a laptop with hot-swappable bays. That kind of interactivity, while not needed as much now, reminded me of an Apple that loved cool ideas and made them happen to the betterment of their customers. Apple has used a variety of materials for the iPhone so it should not be a big deal to consider it. (I wonder if they could do a limited edition glass model iMac...) Given that Apple's cash cow is phones and services, they shouldn't be so afraid of letting consumers upgrade their Macs and keep them longer. The lifecycle here would be 4-7 years.
Further, they should reengineer the keyboard experience. It's not enough (or really, desirable) to slap a touch bar on the current keyboard (which they'll probably do anyway). I've yet to see an affordable third-party option (and one that's not Windows-centric) that I like. For one, I'd like better keys: They keep getting a lower profile and, by extension, have driven up error rates (cutting productivity and satisfaction). I like my 2007 keyboard fine, but the newer keys are thinner and harder to use. There have been attempts over 20+ years to add media and app keys to keyboards. I'd be interested in a swappable module to change/flip the numeric keypad with a touch screen that could be app/OS context aware. I'll add that I have always hated how the headphone jack went from the front to the back: Why not just have a headphone jack on the side or back of the keyboard? Well, that will never happen now - we're lucky to just get a headphone jack at all. Perhaps they could explore a combination of tactile keys and buttons with dynamic labels. And please, backlight the thing.
Finally, color. Aluminum gray is the New Beige: It's time for Apple to renew the excitement of their machines instead of wallowing in the dower blacks and drab grays that exclaim dullness with all the pop and verve of Eeyore. That they've continued this pattern since a year before Obama accepted the Democrat nomination (in '08) is telling.
It's time for Apple to step up. We're starting to feel different about you - and it's not a good feeling.