No, there's no need for NBC to change the format of Saturday Night Live. Since the first show aired in 1975 the show's blend of comedy, commentary and music over the course of 90 minutes has had its high moments and low ones, but over the years the show has consistently delivered an okay entertainment experience.
I believe that the format of Saturday Night Live should not change. I think it is really funny when the host comes out and does a monologue. The short sketches are funny and don't lose the audience. Having a musical guest always breaks up the comedy. The show has lasted many years as further proof that the format does not need to change.
"Saturday Night Live" is a popular American comedy show and it the format should not be changed. Fans appreciate the style of sketch comedies, monologues, and musical performances that have made this show popular for decades. No one wants to see any major changes in this late night staple program.
Personally I've read pages of the dictionary that are funnier than Saturday Night Live, I think saying the show reaches for the lowest common denominator would be giving it far too much credit in how clever it is. That said, the ratings don't lie, it has a loyal fanbase and it does well, so as long as it's comfortable with its market, why change?
I think that the format is really good and it shouldn't change. They really just need a new influx of talent because a lot of people have left them that were the cornerstones of the show. I really like how they involve celebrities and current bands. I think it's fine.