I think it would be interesting to see Apple incorporate their iPhone colors (S models, not C) into their Mac line.
Not saying I think it will happen or anything, it would just be interesting
I think it'll happen. They have avoided it for so long, but its now getting to the point where the lineup is stale. Sure, we get new models (rMBP for example) but the overall design hasn't really changed in a long time now. I dont want them to ditch the current design as its very nice, however offering it in different colors seems the next logical step.
I get the feeling that under Jobs it wasn't even allowed to be discussed. It took them long enough to offer a white iPhone.
It'd be really great if some bold colors could be done with Aluminum, without it having to be a coating, which scratches or flakes off eventually.
I don't think we'll see plastic macs anymore though. The Mac's aluminum works as a great heatsink, and allows them to have the fans running much slower (and quieter) than on comparable plastic laptops for example.
The rMBP is a great example of how the case is the heatsink, and it works very well. Right now my rMBP has Photoshop, XCode, Sublime Text, Chrome (approx 35 tabs), Spotify, and MySQL Workbench open. They have been open for approx 2 hours. iStat shows my CPU temperature as 60c, and the enclosure base (3 sensors) averaging 36c
In comparison my old white plastic MacBook would run hotter than that when idle.