Would there have been other 'Thin Man' movies?!

There was actually a point at which the studio planned to make a 'Thin Man' movie without Ms. Loy. When the studio initially wanted to begin filming the third installment, Myrna Loy had postponed her career to serve the Red Cross, I believe, in war relief efforts, and she refused to make the film at that time. They even had another actress lined up for the part but wisely thought better of it, and the third film was made later with Ms. Loy in the part.

However, you are right; Ms. Loy was fairly disgusted with the quality of the last few 'Thin Man' installments. Myrna Loy's autobiography, "Being and Becoming," details all of these occurrences. It is an excellent read, and I am grateful that I took the time to enjoy it.

Well, Woody didn't direct the last two, so more would have been possible without him. However, Hollywood and the audience recognized that the franchise was running out of steam. After The Thin Man Goes Home, they were saying it was time to hang it up. Powell was in his 50's and the banter seemed more suited for the 1930's than the war-time 40's. With Song of the Thin Man, the complaints magnified and I think all concerned recognized the franchise was done.

I love all of the films but admit they grew weaker as they went along.