In the parallel thread in the SQ forum, somebody pointed out that the Amex Membership Rewards to SQ ratio is still 1:1.
While that doesn't help those of us that have lots of SPG points, it is an option for some moving forward if your target is SQ. Of course, there's no guarantee that MR:SQ will remain at 1:1.
http://www.flyertalk.com/forum/showthread.php?t=813715
-David