There is supposed to be 6 months' warning before changes to the RR program, as I recall.
EDITED: I was remembering this from a couple years ago, but it's been changed, which I only vaguely recalled. The new rule is #40 here:
http://www.southwest.com/rapid_rewar..._and_regs.html
"Southwest Airlines reserves the right to amend, suspend, or terminate this program at any time, with 30 days' notice."
So having a pile of AMEX or Diners points waiting in the wings, ready to dump into RR if advisable, may not be a bad strategy. I presume you'll get the 30 days to grab a pile of RR credits. Better check in here every week or so, because when the change comes someone will post it here.