Possible? yes, and (for me) it was a smooth install. It sets itself up in a separate folder hierarchy and doesn’t conflict. I have DS2/3/4Pro installed, and happily coexisting.
The Problem I’ve had is PEBKAC (Problem exists between Keybaord and Chair) so that my content directories are all screwed up…. my problem of not really knowing what I was doing at the time, and being a dabbler, rather than really learning the hierarchy of the content.
My main suggestion will be to make sure if you want to “merge” the content directories or keep DS3 and DS4 content libraries separate, and then proceed.
I am still looking for that magic button that will scour all my content directories - DS2/3/4 Poser 4/6/9 - and combine them all into one (or two) convenient locations.