Skyward Sword actually didn't use strictly live orchestration. Boss fights, cutscenes, and a few jingles did, but every other song -- well, except for Levias's theme -- had orchestration mixed with MIDI. I love this style. Believe it or not, MIDI actually sometimes works better than live instruments to fit a mood or setting. However, pure MIDI just sounds outdated, which is made very clear by Twilight Princess's soundtrack -- the music itself wasn't bad at all, but it used MIDI that was supposed to sound like orchestration, which wound up making it sound exactly like what it was: an imitation. So when you mix the two, you're free to use MIDI in appropriate situations while avoiding an outdated sound. This is definitely what the series should go with from here on out. It's too cool of a style to leave behind.
As a bit of a tangent, the series also needs to keep up the kind of music found in Skyward Sword's soundtrack. Past Zelda music was good, sometimes even great (especially ST), but SS's was of the utmost caliber, joining the ranks of soundtracks from games like Metroid Prime, Kingdom Hearts (series), Mega Man Zero, and the Super Mario Galaxy games. Naturally so, considering Galaxy's composer, Mahito Yokota, was the lead composer.
