FL Studio mobile is already quite capable, and I'm sure Logic for iPad would be great. But most DAWs make heavy use of plugins/VSTs to provide extensibility to the environment, and I highly doubt that will be supported. Why would you use an iPad over a MBP for that kind of thing? I can't imagine the touch-screen gives any sort of real advantage.
iOS does support audio/synth plugins in the form of AUv3, it's a little bit clunky but works.
I work primarily with Logic (been using it for 20 years) but the form factor of an iPad is pretty nice - it fits perfectly on music stands and laptops don't. If Macbook screens would tilt 180 degrees, all the way flat, you might be able to use them on music stands too - but they don't.
If you are both playing and recording a real instrument at the same time, having the iPad on the the piano/music stand in front of you is very useful. Many people use Logic Remote on iPad on the stand, and Logic on MBP for actual recording at the same time. But not sure why you should need two devices.
Touch screen is nice for some things too, like mixing or quickly toggling things.
