Teardown Slices Into Apple 5K iMac, Upgrades Are Tricky, Not Impossible
In a word, no. However, there are some upsides to the iMac's overall design that DIY repair folk (and upgraders) will appreciate. The folks at iFixIt got their mitts on the new AIO and gave it the teardown treatment, noting that it's still incredibly easy to swap out the RAM. There's a slot in the back that pops open, and Apple even provides a diagram on how to remove and install the modules -- that's fairly uncharacteristic of the Cupertino outfit, which typically goes out of its way to keep customers from mucking around inside its products.
Unfortunately, replacing the RAM represents the end of the road on Easy St. To do anything more, you'll need a "steady hand" to cut through the double-sided tape that holds the panel in place. You can purchase an iMac Opening Tool to make the process easier, though you'll still need to replace the tape when you put it back together, as well as supply your own nerves of steel (this is a $2,500+ machine, after all).
Once inside, you'll see that the 5K 5210x2880 display is made by LG. You'll also find plenty of modular bits, including the hard drive and, surprisingly enough, the CPU -- it's not soldered to the logic board, so there's an upgrade path there.
When all was said and done, iFixIt gave the new iMac a Repairability Score of 5 out of 10. On the plus side, the RAM, HDD, and CPU are all replaceable, and many components are modular. However, the iMac lost repair points for having the 5K panel's glass and LCD fused together with no magnets holding the glass in place.