To switch or not to switch is really a very personal thing.
If money is not a problem just switch.
Sometimes, I know it is frustrating to miss some shots due to your equipment limitation.
But think again, can we captured everything ? The answer is no.
I am so far still happy with my Nikon system.
Occasionally, I will have the urge to own a Canon, Pentax, Sony or Olympus.
However, after much self consideration, I still decide to shoot with what I already have.
End of the day is the photograph that matter most.
Of course, one day if I can no longer control the urge to switch, I will just buy if I can afford, and enjoy the new toy.