Well we saw in that past that support can be based on the developer (black ops series being on wii but warfare not).
I don't think install base has anything to do with the last game skipping wii u. If Wii U never see's another COD game its to do with Activision assuming the right audience is not on the Wii U and I'd say they'd be right. Especially come fall 2015 I think anyone who really wants to play COD will do so on X1/PS4/PC. I can't see the Wii U version doing more then a few 100k.
To be honest I don't know why Activision doesn't port to Vita. If Declassified can top 1m whilst being one of the worst games ever made, there is obviously an easy market for a solid port.







