I’m not sure many of us are qualified to answer this question—myself included. I picked up the ukulele to start teaching it, and I’ve played (in a sense) guitar for many years. I never connected with the guitar, even though I’ve taught it in class at the high school level.
When I introduced ukulele to my middle school students, the potential of ukulele as a transition to guitar seemed logical. I also know schools that teach GCEA ukulele in grades 6 & 7, DGBE ukulele in grade 8, and offer guitar in high school.
When I went through college as a music educator, ukulele wasn’t considered an instrument for schools. We were taught guitar, recorder, and African drumming. This was the mid 1990s, and the ukulele didn’t begin its next Renaissance until 2005 or 2006. Knowing what I know now, I might introduce ukulele instead of guitar—and I’d certainly be requiring all elementary educators to learn it as well (in my thoughts, music should be a part of elementary education throughout the day...song can be used as transitions, etc.).
Simply put, I’m not sure many people on the mainland US played ukulele between 1964 (Beatles first Ed Sullivan appearance) and 2006. On the other hand, MANY people are learning the ukulele today, and it will be interesting to see if they stick with the ukulele and add guitar, or transition to guitar, or leave music altogether.
Playing ukulele would certainly help as you learn barre chords (partial and full), and would be somewhat of a logical transition to classical guitar. However, metal strings on an acoustic or electric are still going to hurt more than a ukulele’s ever will.