The problem with that of course is that in Dominions, the 'magic' (probably we would call it science) is something which could be researched. That being the case, you could also argue for it becoming more powerful in much the same way we went from the bow and arrow to automatic rifles.
I'm not so sure all is death in the future of Dominions, well, unless your on the losing side in the battle to become God
. Older empires are dying, much like Rome did, but other Empires appear to be doing fine. I get the feeling it's moving towards the stereotypical "time of man" concept you get in much fantasy, where the humans exterminate or out compete everyone else.