One thing I do is to save images being worked on in a "In Process" folder with a new name. Once all the adjustments are done then the completed image is saved in a "Processed" folder with the same name as the "In Process" folder name. This preserves the original NEF image and name in the (Lightroom 4) catalog and gives me a new file, in the "In Process" folder, to work with for creating a jpg, tiff, or whatever additional processing.
Once the image is completed and saved in the "Processed" folder for whatever venue I need (Nikonians, Cambridge in Colour, print, etc.) then it is deleted from the "In Process" folder. What's left is the original NEF in the LR4 catalog and the finished image in the "Processed" folder. If I wanted to use a new and different process I can go back to the original version located in the LR4 catalog and go through a different process and make another image. Perhaps posterized this time.
Maybe this sounds complicated but it works for me and I know I can always go back to the original.
The "Processed" folder could be further sub-divided for Nikonian submissions, Sold, Printed, Web images, etc. This would tell me what the image was for and when.
While I've looked for how the pro's do image management I've never really found anything so, like Sinatra, "I did it my way".
BTW, it doesn't make any difference which image processing software I use I can still do the same. If I use LR4 or CNX2 perhaps I could append something in the image name, or folder name, to reflect which app was used for processing. Typically I use LR4 for cataloging and CNX2 for processing.