My question is, since our final output is a standard definition DVD, is there any advantage in upgrading to a high definition camera?
Funny you should ask this. Over the holidays I finally created my first high definition iMovie and then burned it to DVD using iDVD. I'd read somewhere that it was better to edit in HD and then let the software process that into a SD DVD. I didn't know what to expect when I popped it into my DVD player but WOW, WHAT A DIFFERENCE. The difference in quality between the DVDs I'd created using the same software but with video from my SD camcorder and the quality of the down converted video from my Canon HV20 was stunning when played on my high definition TV. The "old" DVDs weren't all that clear but this "new" one were sharp like the movies I buy. And having it wide screen was great.
But I must be fair. I author DVDs as a job and our SD broadcast quality cameras and video edited on AVID software creates files that are very sharp. I "roll my own" DVDs using DVD Studio Pro and the video quality is equal to that of a commercially purchased movie. I guess these actually would be called commercial videos except for the fact that I work in a higher education setting.
So, my answer? Uhhh...I dunno. LOL I think if you're getting really good quality right now with your GL-2s, then I don't think it would be worth the money for you to switch. Remember, you'll need quite a bit of computing horsepower to edit the video, not to mention drive space. But if it comes around where you need to replace one or both camera, you might think of upgrading to be prepared for the future.
I hope I helped at least some with my rambling.