Nexus sounds great, but I'm pretty sure the name has already been copyrighted by another company for some completely different product. The reason, I believe, Nintendo Nexus sounds so good is because you have the repitition of the "n" sound, which is very appealing to the ear. Anyway, I think the next Nintendo console should not include the words game, cube, or Nintendo in the main title (we should be bucking the trend of naming successing consoles similarly to their predecessors, like Sega's been doing). Here's some ideas from me:
Infinite
Nemesis
Proxima
Xeon