If they're smart and willing to put a modicum of effort into it, they should give them several display options. Given the relatively low resolution of DS they should be able to display games comfortably on both the gamepad and the tv and any combination there of including multiple options for each.
Whatever the case it is indeed about damn time they offered these. However they seriously need to consider a lower price point for the whole virtual console thing in general. 5$ for a NES game and 8 for a SNES game is a bit of a tall order considering the total lack of portability. Not to mention varying price pints based on content. I could see paying 5$ for Final Fantasy or Dragon Warrior, but the same price for Mario Bros.? To quote David Duchovny in the PS2 X-files game, "Now that's just bullshit."