Word on the [Main] Street (at least out here on the west coast) is that the Talking Mickey actually requires two cast members, one in the suit and another in an audio/video booth to do the voice. (Think Turtle Talk With Crush but with a walking Mickey character, I'm told.) This limits Talking Mickey to established indoor meet and greet locations, such as Toontown at Disneyland or a defined D23 meet area (the only other places we've seen him until this week in Orlando). That means Talking Mickey costs a lot more on tech and labor costs for the company to put out there than a "regular" Mickey.
But if that makes a visit with Mickey a more popular attraction for Disney guests and would-be Disney guests, Talking Mickey would be more than worth the extra investment.
Now we sit back and wait for the inevitable YouTube of Mickey verbally smacking down some hecklers....
Another example of Disney's commitment to interactivity at its theme parks. Whether it is a thoughtful word from a cast member at a popcorn cart, a guest being pulled from an audience to participate in one of the shows or a chat between Mickey and a child, the interaction that immerses the guest into the "show" is why Walt Disney World is the gold standard for themed entertainment.