Sure you can, but that would be kind of pointless, especially since the existence of the train would make development, construction, etc. harder as they'd have to work/plan around the train tracks -- I think it's pretty unlikely Disney would want to keep the train if they built a new land up there.
It would also be a relatively long walking path if it was all the way up at Rafiki's current location, so they'd probably want shops, QS, or something else along the way so people weren't just trekking through empty space. The train would be a hindrance to that too.
Not that they couldn't work around it (obviously they could), but I don't think they'd consider it worth the hassle.