To me, it's pretty tough to beat the "laptop / dumb music player" combo.
The laptop can download songs on the fly, rename them, edit and normalize them on the fly, and so on. (Maybe you guys think that's lame, but I like to be able to snag requests at a gig.) You can even use Youtube in a pinch since Internet is basically everywhere now. (You can also tilt the screen for optimal viewing, of course.) Then the dumb player can simply focus on what it does best.
The half-dozen controllers that come out every month will always and forever have compatibility, standardization, and configuration issues. That's my prediction. Meanwhile, a control signal is a control signal, whether it comes from a cassette tape, an iPod, or vinyl.
You do have to be careful with a laptop but they're pretty much a commodity item by now, plus I'm not sure a Macbook is any more fragile than one of these CDJ2000s which has a full computer, including networking, inside it. And, before much longer, professional-level DVS software will run on phones, tablets, you name it -- so the convenience barrier will be even lower.