Really? It's only .7 miles? I was measuring it as a little less than half a mile from where you board the train. Regardless, the comparison with EPCOT isn't a good one because you're walking through the park and by attractions etc. (well, maybe not at the moment...). My imagined walk up to Planet Watch is by a whole bunch of nothing.
I didn't realize all of that land behind the Jungle Trek and Kali Rapids was usable for Animal Kingdom, though. Of course, if that's all developable land, then they don't have to do a ton to Planet Watch (especially since, again, it houses all the vet facilities). Develop all of that land and Planet Watch is something people can walk to/is next to other areas of the park, rather than being an isolated area with no access other than a train.
They should plus up Planet Watch and maybe add some other activities (although I imagine the Animation Experience would be a pretty big hit if it didn't require a separate train ride), but they wouldn't need to demolish and replace it -- which is something I don't think they would do anyways because of the vet facilities.
The point of walking there is that all the unused land is transformed into attractions. Until then, you have the train.