This is an ongoing investigation: Does (NCL) Nintendo HQ use sales numbers from Japan only when they decide which games that are worthy of a sequel?
So far it seems as that (with a few curious exceptions) a console game for a Nintendo home console have to sell close to 1 million copies - IN JAPAN - to get a sequel. Games with Mario in the title can sell a little less.
This explains why we get Mario Tennis (N64 - 1060k) instead of Mario Strikers (GC - 200k) , Mario Sluggers (GC - 260k) or even Mario Golf (N64 - 650k). This explains why there are rumors of Diddy Kong Racing (N64 - 890k) and that it was so hard to get Starfox (SNES - 800k). Other sequels we probably can forget are Metroid 3D (best selling 3D Metroid in Japan is Metroid: Other M -130k), F-Zero (SNES - 890K), Wave Race (N64 - 340k), Pilotwings (SNES - 480k), Mario Paint (SNES - 710k), 1080º (N64 - 130k), Endless Ocean (Wii - 120k). This could have been a major component in Nintendo not fighting for Rare. Except DKC Rare did not sell well in japan, not even Banjo (N64 - 550k)
If this rule is true there is a bigger chance of Rhythm Heaven U (Wii - 770k) than Metroid 3D U. Metroid 2D could happen though (NES - 1040k)! Even games like Mario Galaxy (1020k & 980k) and Luigi's Mansion (Wii -460k) could have a hard time getting a sequel. This explains why Twilight Princess (Wii - 600k, GC - 40k) is the Zelda game that will not come to Wii U (remake or VC).
Strange exceptions: Xenoblade Chronicles (Wii - 160k), Fatal Frame (Wii - 100k), Fire Emblem (SNES - 700k)
Please fill in with your own examples. I will try to come back with more numbers and "proofs".
EDIT: This also means no sequels to Splatoon (~300k), Captain Toad (150k) or Hyrule Warriors (130k).
