I think that the best approach for Smash 4 to take would be to show love for all generations of Nintendo games, not just "updating" everything to match whatever the latest game is in each series. I'm not saying we shouldn't have Mario Galaxy or Skyward Sword stages; I'd love those. However, I also would love to see new stages based on Super Mario 64 and, say, A Link to the Past.
I feel like Smash (or at least Brawl) has this tendency to focus on only the very recent and the retro. The Donkey Kong stages introduced were based on DK's most recent mainstream game, Jungle Beat, and the iconic original arcade game. Mario stages have shown a trend toward being either "retro" stages such as Mario Bros. or Mushroom(y) Kingdom, or based on Mario's most recent hits at the time (Delfino Plaza). Pertaining to Smash 4, this becomes a problem with series that haven't had a game since Brawl (and many haven't), or with series that haven't had a game since before Brawl (like Ice Climber). Nintendo has slowed down its growth since Brawl's release, and we haven't seen the sort of booming activity of the development of classic and new IPs that pervaded the period between Melee and Brawl. I think the best route to take is to try and best represent each series through their most iconic material from throughout their histories. There's nothing that can really be done to update the F-Zero content, for example, but there's still plenty of content the series has to offer that can still be tapped into. The same goes for just about every series.
Now, what do I expect? I expect two new Mario stages: one based on the Galaxy games, and the other on the aesthetic style of New Super Mario Bros. and Super Mario 3D Land. I expect a Skyward Sword stage for the Zelda series, and possibly Skyward Sword character designs, but I also think the Pirate Ship will return to tie in with the Wind Waker re-release. There will be a Donkey Kong Country Returns stage. Star Fox will pull from its 64 success and revert to those character designs, and include a stage based on that game. F-Zero will probably just use another course from GX to craft a new stage. Wario will take ideas from WarioWare DIY and other recent releases, though I really hope they give Wario Land Shake It! some love. I definitely agree with Sonic's stage being based on Sonic Colors. Sonic Team seems to have adopted that game as their flagship title, and reference it non-stop. I think the stage will be Planet Wisp specifically. It appeared in Sonic Generations, and also represents the gist of Colors pretty well. It's a location familiar to Nintendo gamers because of Colors' Wii and DS exclusivity. The mix of forest and factory in the location also represents the environmental vs technological theme of the Sonic series pretty well. The other guest series, Metal Gear, I predict will take most of its cues from Metal Gear Solid 3, because of its presence on the 3DS and the series' recent focus on Naked Snake. I can see Naked replacing Solid, but using the same moveset and name, basically no differently from how the transition from OoT Link to TP Link was handled.
