I am holding on a 2012 iMac. It had become unusable with the original HDD, but I upgraded the RAM to 16GB and installed a SSD a few years back, since which it has been quite reasonably functional. I would still like to upgrade, but the white bezels are on the 24", are putting me off as long as there is no emergency. I would also happily go modular, doing a mac mini + monitor if there were a reasonably priced branded monitor. But, that is not the case, so I'll continue to wait. For a while, it would seem.