Hmmmmm.

In actuality I did not assume "that CP won't devalue again." Yes I did make an implicit assumption that there will be no future zero-notice devaluation. (It is not unreasonable to believe the one last summer was due to extraordinary circumstances.) As long as there is notice of a future devaluation the redemption can be made at the recently announced exchange rate. It is important to note that, on the flip side, I also considered but did not mention that SWA could very easily increase award extension fees. They recently doubled their baggage fees with minimal advance notice. When they increase the award extension fee can we be sure we'll be able to extend at the old rate? IIRC, we have to wait for an award to expire before we can extend, so even, say, six months notice of a fee increase may not save us.

I haven't read anything about why the current change was made. Two possibilities come to mind. One is that SWA increased the amount they charge partners for RR credits. Another is that after the Amtrak-related fiasco last year, CP suddenly took note of how many of their points are redeemed for RR credits. They did the 20% devaluation to immediately stem the tide, then continued to monitor the situation. Eventually they realized that even at 3000 points per RR credit the exchange program was costing them too much. There could be another devaluation in the future, but if so there will in all probability be a "watch and wait" period similar to the one recently completed.

Unfortunately for them they will probably see a business drop off and an other income drop off...both of which they will likely blame on the economy instead of associating it with their business policy changes.