Why would "a Gamestop employee" know this anyway? Or even "the store's Nintendo representative"? Statements like that are always dead give-aways as far as I'm concerned.
It won't be shown at E3 in any way visible to us.
Anyway, nothing too far-fetched, anyone could guess any of these things and be right. Like, 'fast-travel', 'different day/night enemies in the overworld' and Gorons are all no-brainers. Pro Controller support and amiibo giving an item a day also wouldn't be surprising since Wind Waker HD and Hyrule Warriors also have that respectively.