Sorry about that.... To be more specific:
Current System:
iMac 27" - (Mid 2010)
3.2 GHz Intel Core i3
16GB Memory
System I'm considering:
27.0” 5K retina - (Late 2014)
Quad-Core i7 4.0Ghz
Fusion Drive 1TB - 16GB RAM
This is ... QUITE A BIT ... different than the specs you claimed in your initial post ...
There would be a **very** noticeable difference in performance between these two machines. A Core i3 and a quad-core i7 aren't even in the same ballpark, particularly in terms of performance on apps -- like Adobe's CC suite -- that can fully leverage multiple processors. And this is before we get into the much improved graphics system, which CC are highly dependent on.
We'll also further ignore for the moment how much higher-resolution, color-balanced and gorgeous the Retina 5K display is compared to your current iMac. And the fact that the Fusion drive will perform approximately 5x-8x better than the spinning-platter HD you are likely now using, though of course you could stick a 1TB SSD in your present machine for an even greater boost in that department.
Oh and then there's how much more RAM you can upgrade to in the newer machine ... and how much longer (four revisions longer) you'll be able to keep OS and software updated ...
In case you haven't caught my drift ...
If you're in a position where you can get the newer machine ... it's a no-brainer in my opinion, UNLESS and ONLY unless you expect to be in an even better position a year or so from now. Then (if I were you) I'd replace the HD with an SSD and carry on for a year or two, THEN get whatever 5K Retina iMac they are selling at that point.