There haven't been any new dates set that I'm aware of. This is how I remember it. They've relied on very strong "suggestions" of when the end might come. After 1975, the other major card they still had in their hand was the generation card. The teaching that people that were old enough to remember the events of 1914 would still be around during Armageddon morphed into the teaching that people that were simply alive during 1914 would be alive during Armageddon. They used a scripture that said that a generation is 70 to 80 years to lead people to believe that the end would not come much later than 1994 (80 years after 1914). Of course, they never specifically said that end will come before 1994, but any JW with half a brain could do the math themselves and figure it out. There was actually one magazine that actually said that the end would come before the end of the 20th century. They later changed that in the bound volume edition. Apparently, it was an "oversight" by the teaching committee.
Well, 1994 came and went and nothing new happened. The next year, 1995, they came out with "new light" remaking the generation teaching. They said that the generation that Jesus talked about in Matthew 24 was not one of these 70-to-80-year generations but rather a more generic generation that amounted to an era. They reinforced that the end was still very near, but we could no longer say that the end would happen 70 to 80 years after 1914 (duh, it was 1995 already). The generation teaching is virtually meaningless now and is seldom ever brought up in the publications anymore. I think this let the wind out of the sails of a lot of JWs that were paying attention. Many publishers didn't have any idea that that Watchtower study was really significant.
Ever since, the Watchtower has been reminding everyone of just how close the end really is. They publish articles that use other ways of "proving" that Armageddon is just around the corner. For instance, they'll say stuff like the book of Daniel lists 7 world powers and we're living in the last world power listed, so the end must be near. Daniel talks about the eighth king that would rise for a short time, which they interpret to be the UN, so the end must be near. What's lost on a lot of witnesses is that the Watchtower makes up the rules about how to interpret these prophecies, so they aren't really proof of anything. They could change the way they interpret them tomorrow to "prove" something entirely different. A lot of witnesses, in my opinion, began to sense that they were really in it for the long haul and began doing things like getting an education, saving for retirement, etc. In response, there have been a lot of talks vilifying higher education. There has also been a big push by public speakers at assemblies giving the impression that the end is just around the corner, days or weeks away. There was a Bethel speaker that put his notes down and said that he was going to have a heart to heart with the friends to tell them that he knew how the governing body felt and they felt that Matthew 24:14 had been fulfilled. These tactics are more effective because there's no embarrassing paper trail left when they turn out to be wrong. They can just blame some overzealous brother.
I hope that helps. That's my recollection of how things have unfolded.
