They had the 3DS at PAX East a couple of weeks before it launched in NA.
I think in recent years a lot changed when it comes to consoles being shown ahead of launch.
back when the 360 launched they had just normal demo kiosks in stores weeks before launch. the first time I played a game on 360 was a few weeks before launch in a MediaMarkt. they didn't have any game in it yet, so the only thing I could play was Hexic as it was pre installed even in the demo kiosks.
then a few days later I came back to the same store and they had Tony Hawk's American Wasteland in it.
the DS was also playable in normal stores ahead of launch. they had demo kiosks with Wario Ware and Mario 64 DS in it.
then a generation later and the only pre-launch stuff was at trade shows and conventions.