I think the sequencing of mainline games and spinoffs has been fine -- it's more an issue of quality of the spinoffs. If it's a low quality release, I'm not overwhelmed with too many Mario games in a given time - I'm underwhelmed by a franchise that deserves better.
I've always thought a fusion of Mario Party and New Super Mario Bros or Mario 3D world would be great
I predict NX launches in 2017 - not 2016