In the future it is likely that the differences between Poser and Daz Studio will broaden.  Daz Studio is soon to have dynamic cloth--I'm not sure if it will be compatible with Poser dynamic cloth.  So as things continue to evolve I don't think it's a stretch to forsee a time when thinks have to be specifically designed for one or the other program.  Right now almost everything you can use in Poser you can use in Daz Studio with some tweaking.  A texture map is a texture map is a texture map, unless you have a texture that is soley based on Poser's node system if can easily be used in Daz Studio without hooking it up to the shader tree.  There wouldn't be that many compatibility issues.

I'd be more concerned with e-frontier releasing a new version of Poser that is incompatible with Daz Content.  Most people use Daz Figures and perfer them.  Could any of you live without  Victoria, for instance?  There are storm clouds on the horizon, as e-frontier won't release Poser 7's SKD to make Carrara's transposer compatible with Carrara 5.  So unfortunately we're likely to see more, rather than less compatibility issues, in that case I wouldn't  be upgrading.