I have a recently acquired 632-2. It is very similar to the other "hammerless" J frames. I suspect the lack of a lock on the "hammerless" Js is due to configuration and not any other reason. The geometry of the hammer-trigger-sear relationship is different than in "hammer" J frames, as is one of the reasons that I like the Centennial models action so much. BTW the 632-2, called a "pro" model for some reason is a really dynamite revolver and is the only one that has come close to getting me away from my 940s which I regard as the best J frames ever made. It is very accurate, and if what it did to some water jugs is any indication, it should totally ruin a bad guys day. And its recoil is on a par with the 940, or a little less.
As far as future locks are concerned, I had the oppertunity to speak with some S&W folks at the factory a while back and the word that I heard was "look for locks", they are not going away. It would be quite a legal struggle for S&W to explain why they put locks on most of their guns, then took them off.