Would you buy an iMac with a larger screen? Like say 32-inch? Wish this was the case with the 5K iMac.
Yes (well, no, because I've only just bought a new iMac, but yes in the hypothetical future).
I've used a 4k 28" screen and while the extra inch is a small difference, it is worthwhile, especially if you set the "looks like" scaled resolution a notch higher than the usual 2560x1440. 4k at 28" is definitely still "retina class" so 5k is still going to be perfectly sharp.
If Apple's industrial design magic is as good as they think it is, they could shrink the bezels on the iMac and fit in a 28-29" panel without significantly increasing the physical size of the case.
The other thing they could do is lose a bit of chin and make the display a bit taller - 16:10 instead of 16:9 - i,e, 5120x3200 - i.e. a proper pixel-doubled version of the late lamented 30" display.
Of course, 5k displays don't seem to be catching on outside of the Mac world so they'd have to get a specially-made panel the result might be a bit expensive...
However, what I'd really,
really have liked better than a 27" iMac would have been a Mac Mini with a comparable quad-core CPU and GPU so I could have chosen my own displays. The iMac's 5k screen
is a thing of beauty - but 4k is still pretty good, and I'd like to be able to use my main display with other computers from time to time.