I'm not really thrilled about it being for a specific phone that is likely to have a physical form factor not guaranteed to have any particular lifetime.
Even with that... the non-iphone versions they previously sold were thousands of dollars. This is a huge leap in affordability even if you have to buy an old iphone 5 to go with it.
They address that in the FAQ with something like "you can always keep your iPhone 5 around as long as you need to use this if it doesn't fit the iPhone 6"
In my opinion, it wouldn't be that hard to adapt to a wider iPhone. It's two pieces: a case with a hole in the back for mounting, and the camera brick - which only touches the back and bottom of the phone.
For instance, the E4 they sell is $1000 and up.