The problem with space travel is how modernized the setting of a Zelda game can be while retaining the same franchise feel. There's nothing wrong with having primitive guns in Zelda either but including an AK-47 for example would be plain ridiculous.
Space also provides the franchise with a setting completely different to the ones experienced heretofore. Every installment thus far has been based in a universe similar to the Earth we humans populate. This allows the player to better relate to the experience. Zelda has evolved through a dynamic shift from 2D to 3D, new transportation methods, and most recently heavily integrated motion controls, however, none dramatically altered what the franchise was known for. Zelda certainly should not be the next Starhawk.
It's pretty far from the Earth we humans populate, that's what always pulled me in was this fantasy world that I can escape to for a couple hours and if it changes drastically but still retains some elements then it's cool with me. I've been playing Zelda for years now and would be excited to see Link set foot in new territory that isn't a dark world or just some messed up version of Hyrule with all the same sprites.
Every time I hear about new ideas from fans about what they want to se ein Zelda it's always the same thing. Everyone wants another dark world for Link to go to, everyone wants at least an element we've already seen but nothing new and exciting. Like I said, Hyrule isn't that different from our world but if you want to think about it realisticly it's a changing world, a world that can't stay the same forever and if Nintendo is smart enough they can pull it off without killing the franchise.
Hyrule has been evolving but slowly since the first game, we haven't seen anything drastic other than a change into 3D or a few robotic figures in the game. The experience I've had thus far with every Zelda game was that I was doing something I can't do in the real world, so I can't see why anyone would want to relate to the atmosphere we experience outside of the game.
If Nintendo loses a few Zelda fans then so be it, but they would gain a new audience or open doors for fans that are having doubts.
