And I also just remembered that this is the beginning of April. Typically in April and October, there are major shakesups with the schedule; same thing goes with cable channels in general.
In April 2009, GSN lost the blanket licence on the Goodson-Todman library, so now, they only lease for portions at a time of them from Fremantle. Likely in this situation, it was renewal time, and only Match Game, Card Sharks, and Press Your Luck were getting the best ratings, while GSN decided ratings for "Sale" and "$25K Pyramid" weren't good enough for renewal.
I'm sure both shows will return eventually.