You'll still have titles on the U for the hardcore crowd. ZombiU looks great and has a nice game mechanic that has you switching protagonists when you die. Your previous protagonist is now a zombie and you have to find and kill him to get your survival bag. Great use of the touchscreen too.
Nintendo have plenty of franchises to appeal to the hardcore crowd, the biggest two will be the titles that Retro and Monolith are working on. Very disappointed that we didn't see anything of them though. You've also got the likes of Zelda, SSB, Metroid, F-Zero, Wave Race and perhaps Ice Climbers in the not too distant future too.
And there's a difference between hardcore titles, casual titles and titles that will appeal to
everyone. People often get the last two mixed up. Luigi's Mansion, Mario Kart, 2D Mario games and 3D Mario games aren't casual titles. They are mainstream titles designed to appeal to everyone.
Edit: I'm very pleased to say that ZombiU has kept the multiplayer idea from last years proof-of-concept demo where one player uses the U GamePad with a top-down view to give the player a Dungeon Master type role. Fantastic.