If I am not mistaken some of the Night Guard series feature a 2 piece barrel, along with some performance center models such as the M&P R8.

I also think the reason for hte discontinuation is a combination of resistance by old guard S&W shooters in combination with manufacturing costs that exceeded the initial expectations of a cost savings. Basically, S&W found out that this system cost more than they expected and the revolver buying public didn't care enough about the increased accuracy of this system to adopt it in a fashion widespread enough to make economic sense.

IMO, that's a real shame. I fully expect that in another 10 or 15 years the 620 will come to be regarded as the most accurate revolver S&W has ever produced.