In a nutshell, it seems to me that Fluxus is dead if (and only if) it is defined as a movement in art and culture associated with the group of artists who came together in the early 1960s with George Maciunas at its centre. However, if Fluxus is defined as an approach to art and culture centred around the idea of Intermedia, then it remains very much alive.
I am strongly inclined towards the latter view.
The question may never be finally settled, especially given the tautological nature of the "Fluxus is dead" argument... I.E. If Fluxus is defined as a movement that existed between 1962 and 1978, or between any other relatively arbitrary dates, than the definition itself precludes the possibility that Fluxus is still alive.
The artists who were originally involved in Fluxus' early days have not been consistent either. The sense that I have been able to discern from their statements is that they believe that the Fluxus that they knew and worked in has indeed passed away...but that the ideas and ideals that they worked from continue to live in contemporary art practice, including contemporary Intermedia. So for them the question is, "is Intermedia the same as Fluxus?" Here again I would argue that the answer is, "yes".