I think that some people have indeed changed on a personal level as they witness change in society's collective opinion. Some people are positively influenced because society's trends inspire some individuals to ponder issues and perhaps form new opinions.
I know that's true, I remember when the big 'whisper, whisper - I'm so shocked deal' in my family was that my cousin dated a black guy when she was in college. Not married, just dated once or twice. Now, several of us have Hispanic wives/GFs. Things do change. However, what is acceptable in society still may not be OK in the family. In the same way that most rational people think there should be more treatment centers for drug abuse, but still don't want it built next door.
Its also a huge thing I think, and it takes people a while to figure it out. Even if they accepted it in theory, its different when they are confronted with it. They need time to sort out their own thoughts.
As it becomes more common, as it becomes more and more real to more and more people it will be easier to take I think, but such changes take decades (as in the above deal in my family, the difference between Ohio in the 60s and California in 2008). The first time anyone came out to me as gay I was pretty taken aback. The last two who did, my reaction was more one of "Duh, we all knew that, nice you figured it out."