I can only hope it's not another DSi and becomes a GBC in the long run - the DSi was a wasted opportunity. That being said, consider DSiWare, DSi Enhanced titles, WPA compatibility, a built-in browser and audio player - the DSi was factually better than the DS.
I don't think the 3DS has been around long enough for the N3DS to go the route of the GBC. I also doubt the N3DS is a significant enough upgrade for a lot of people. To me, it's not a big enough upgrade to justify almost $200 over the current 3DS I have. It will differ for people. For those that like the 3D, it's a godsend.
To me, it's another DSi. There were some great DSi exclusives (via DSiWare), but I was fine waiting until the next generation, as Nintendo has reliably added backwards compatibility to their handhelds. There might be some N3DS exclusives I want to play, but I'll probably wait until the next generation, as it will probably be backwards compatible with N3DS exclusives. In the end it comes down to what the OP values:
N3DS: If he/she would rather have a slightly better handhelds experience and possible access to a few exclusives, this is the route to go.
Wii U: If he/she would rather have access to the Wii U library, then this is the choice. It depends on if any of the games in that library interests him/her.
PC Graphics card: Well, can't go wrong with better gaming PC hardware, as there's something for everyone on PC.