Those emulate the Neo Geo Pocket, not the Neo Geo.
Like iq_132 said, it's not going to happen. The Neo Geo is like a Genesis running at twice the speed, with better graphics hardware. The DS is barely powerful enough to emulate the Genesis. On top of that, Neo Geo games are huge (compared to other 16 bit games, anyway). The DS doesn't have enough memory to hold one of the larger Neo Geo roms, even using the extra RAM in a slot 2 cart.