It makes sense for publisher to prepare audience for new games in the series by releasing previous one (or similar one, or at least the one with similar name) on downloadable services. Like with seemingly random Sin & Punishment N64 release on VC that was actually leading up to S&P 2.
Let's look at trends with Nintendo's VC releases and try to guess what's coming next.
3DS Ambassador titles (2011):
Super Mario Bros.
Metroid
The Legend of Zelda
Zelda II: The Adventure of Link
Balloon Fight
Ice Climber
NES Open Tournament Golf
Donkey Kong Jr.
Yoshi
Wrecking Crew
Metroid Fusion
Mario vs. Donkey Kong
F-Zero: Maximum Velocity
Mario Kart: Super Circuit
Yoshi's Island: Super Mario Advance 3
WarioWare, Inc.: Mega Microgame$!
The Legend of Zelda: The Minish Cap
Fire Emblem: The Sacred Stones
Wario Land 4
Mario vs. Donkey_Kong
Kirby & the Amazing Mirror
Famicom trial campaign (2013)
Balloon Fight (NES)
F-Zero (SNES)
Punch-Out!! (NES)
Kirby's Adventure (NES)
Super Metroid (SNES)
Mario & Yoshi (NES)
Donkey Kong (NES)
Also,
individual VC releases.
Yoshi's Yarn explains why Yoshi (NES) and Yoshi's Island are there. They're even releasing Yoshi for second time on Wii U VC.
Fire Emblem was leading up for new FE game for 3ds.
Donkey Kong Jr. , Mario vs Donkey Kong (GBA), Donkey Kong 94 lead to two new DK titles for 3DS in latest Direct.
NES Golf and Mario Golf release on 3DS VC was leading to new 3DS Mario Golf.
Balloon Fight on 3DS and Wii U is probably to hype up Nintendo Land mini-game. Or it's just Iwata giving his game priority #1.
F Zero -- probably also for Nintendo Land
Ice Climbers -- i dunno lol.
Gritty realistic revival?
Mario, Mario Kart, Zelda -- duh.
Wario and Game Watch collection VC releases lead to Game And Wario.
That leaves us:
Metroid -- included in 3ds ambassador and Wii U Famicom trial campaign. Also Metroid 1 and 2 released on 3DS VC.
Kirby -- constant stream of VC releases. Earlier ones can be attributed to two Kirby games in 2011, and but they are still releasing more old Kirby spin-offs.