I want BOTW day 1 on the Switch as much as any of you guys but you've got to remember the context in which Game and other retailers are putting up their advertising. Nintendo posting screenshots every few days, with a bevy of gameplay out there, and with a much hyped Nintendo Switch presentation on the way, it's hard for these retailers to not expect a March release date. However, Nintendo, as of yet, has not said anything other than 2017, and in the 'upcoming games' section of UK retailer game it says TBC. This is the equivalent of an Amazon placeholder date, they've probably got marketing materials printed so they can hype the switch through Zelda, if nothing else. (Source: www.game.co.uk/webapp/wcs/stores/servlet/HubArticleView?hubId=1373251&articleId=1373252&catalogId=10201&langId=44&storeId=10151)
This means that even though all the marketing, from both retailers and Nintendo themselves seems to point to a March release date, there is absolutely no guarantee that will occur. LKD essentially summarised this issue by saying that all formal indiciations (leads/insider info etc) point to a delay, and I think we should give more weight to that than to marketing hype.