Since CPL died, probably? I'm not really sure.
I was a 1.6 player at the time the US competitive scene started lagging away behind the rest and a counter strike editor for
MeetYourMakers so I can tell you a bit about that.
The death of CPL played a part in the fall of competitive 1.6 in North America but what really killed it was the rise (and death a year later) of the CGS. A very american type of competition, with franchises, TV coverage and a lot of money invested in at the time. The competition decided to choose Source over 1.6, as well as change most of the rules of the game that were agreed upon for years to promote "faster paced gameplay" which was more in accordance with the TV format. The biggest teams chose to migrate to source since that's where the money was now. For example, I remember that coL with very skilled 1.6 players such as fr0g became L.A coL and team 3D was New York 3D. It was pretty funny to see that at the time.
Meanwhile 1.6 continued to grow in the other parts of the world thanks mainly to the ESL and events such as the ESWC, WCG and WSVG. The biggest european organizations invested quite a bit of money in their 1.6 teams, and the overall player skill grew immensely. Meanwhile, the 1.6 scene in NA consisted of what I would call "B" teams since most skilled players were looking to get into the CGS franchise system. CGS lasted two years, then closed shop. Some teams tried to get back into the top competitive 1.6 play afterwards, but the train had moved and the skill gap became too much a hurdle for them to overcome so they pretty much gave up.
When I came to Canada about a year after these events happened, I was extremely sad to see the state 1.6 was in. It took me a lot of effort to find a semi competitive team to play with and when I finally did, it didn't last very long. There were still quite a bunch of teams playing at the amateur level (ESEA and such) but it was nothing like the thriving comepetitive scene in the rest of the world.
This is my friends the story of the fall of 1.6 in NA.