Basically release smash 4 with all previous characters and some more previous stages, then reboot the roster and stages and make a more balanced, faster, focused smash for more competitive play. (n4g.com)
There isn't a ton of incentive to return to previous stages unless you're dead set on collecting each stages items. (newgamenetwork.com)
Some people go through these stages in sequence, while others skip phases or return to previous stages throughout time. (tacomachristiancounseling.com)