Maybe some enterprising reporter in Florida will notice a flood of elderly/ailing whose nearest and dearest suddenly recall that Joe/Nancy wanted a quick end versus a long, dreary, and expensive hook up. Once it's so glaringly obvious that the law, such as it is, is being abused, the legislature will be forced to act. The publicity about Terri's case has been so extensive that Florida is the world's laughingstock...again. Worldwide shame and humiliation, at any rate.
Hopefully it won't come to that - one Terri Schiavo is more than enough. I'm not sure what form any changes would take, because, realistically, the laws on guardianship and end-of-life issues work pretty well and are pretty much the way most people want them. There are no easy solutions that I see, but I don't claim to see everything possible either.