This man better have his SFIII Second Impact/Third Strike themes in this game or I'm going to be disappointed. They fit that new Suzaku Castle stage way too well to not be in it.
I'm an avid fighting game player (been playing since Super Street Fighter II on SNES) so I got the feeling Ryu's most likely going to be the most complicated character to learn if they do this like I think they're going to. Just putting him into Smash won't be enough; it won't do him justice as the definitive fighting game character. Just from the leak video I saw a combo that looked like two normal crouching attacks leading into his Tatsumaki kick, so that makes me think he's going to have unique fighting mechanics to him. It looks like Project M Lucario's combo system with some altered stuff. As SF has emphasis on extended normal attacks that create combos, I see him gaining a standard A combo attack, but not only having the ability to cancel into his B moves on hit, but also be able to do a crouching combo attack from his downtilt+A, like the leak video showed.
So that input could be something like, downtilt+A,A then side+B during the second hit for the Tatsu, just like SF. It'll be a bit like the magic series in Marvel Vs Capcom, Darkstalkers or Street Fighter X Tekken when if you press downtiltA,A,A, he will do his crouching light kick, medium kick, then sweep kick/crouching fierce punch attacks for a full slip knockdown/launcher.
Also, I bet money he's gonna have a super meter system (Little Mac basically gives the concept away). I'm thinking since A+B would overlap with the shortcut Smash commands... and considering he's a true fighting game character trying to balance his normal arts and the easy accessibility and wackiness of Smash, he'll have a Two-section (or maybe 4 to properly represent SFIV) super meter. He builds meter by attacking and when he builds a stock then he's able to use one EX special move. If you fill it up to MAX, then you can unleash his signature Shinku Hadouken super move.
B: Hadouken
Side B: Tatsumaki Senpu Kyaku
Up B: Shoryuken
Down B: Focus Attack (Can't be done in mid-air. Hold B to charge, can shield roll out of the charging pose. Full charge attack is instant shield break/dizzy)
...and to do EX moves you have to do traditional inputs from Street Fighter to activate them.
QCF+B (Down, Side+B in quick motion): Shakunetsu Hadouken
DP+B (Side, Down, DiagonalSide+B in quick motion): EX Shoryuken
Down,Down+B: Shinku Tatsumaki Senpu Kyaku (I could see QCB+B working as well if they add a timing window buffer, but I think it would just be easier to do it like this since you turn away from your target in Smash when you press Back and that could be too much of a hassle to execute properly.)
Then for his super.
QCF+A+B: Shinku Hadouken (Similar to his SF incarnation, it's the 5-hit, bigger fireball version rather than then MvC Laserbeam. Have it override the standard Smash command once he has full meter [similarly, this could work for his EX moves, too. As long as he doesn't have EX meter, he can still use the A+B smash command, but once he builds a bar, pressing A+B will do Shakunetsu Hadouken, Side+A+B will do Shinku Tatsumaki, and Up+A+B would do EX Shoryuken].)
Final Smash: Shin Shoryuken (Smash Ball only, activated only with B like always, probably will only catch one opponent, be very limited in range (if not pointblank), but do Marth/Lucina Critical Hit levels of damage & hitback, possibly a OHKO [Star KO] or very much KO on very low %.)
That way, he still has the simple inputs for normal smash users to use, but if you want to maximize your use of Ryu you have to do what Street Fighter (and other fighting game) players do in their native series and learn advanced movements and inputs in order to fully utilize his potential. Fits his characterization and hell, his genre perfectly, while still keeping him Smash friendly.