I like listening to talks by people who are really interested in their topic. I don't get bored or turned off, even if the topic isn't my cup of tea, as I appreciate the speaker's enthusiasm, and like hearing about new things. It's only an hour.
That being said, I do like vintage and antique machines, and would probably enjoy it more if there were pictures or sample machines to look at.
Your guild won't be able to to come up with a slate of speakers that will please every member every time. I think it's a good idea to offer a couple talks that aren't directly quilting related; it keeps it fresh.