I don't think it's an issue of Poser, any upgrades, or its content suddenly becoming unmarketable.  It's more the point of whether the program will be surpassed in ease of use, innovation, development, and content by another program - and at this point that's more likely.

Things to look out for in the future with the various programs include compatibility with subdivision, conforming/adjusting/transferring morphs/scaling (ADS/morphoforms) from figures to clothing/props, optitex (which D|S is working on), node-based shaders (which poser has - Carrara and D|S do not), body-weighting, etc.