Pretty sure the 3DS version sold just fine. Better than the Wii U one, in fact. I wouldn't be too concerned about it failing.I most likely won't get MH4U if that's the case. I actually purchased MH3 on both Wii U and 3DS but I had a really hard time playing it on 3DS while experiencing it with better controls on the Wii U. I ended up putting like 3 hours into the 3DS version. I wonder if MH4U will be the last MH game released outside of the Japan if this fails.
Tri sold over a million in Japan alone.They sold over 500k on the Wii U. Tri on the Wii sold less than a million IIRC.