Well if you are going to shoot bands, folk musicians, and acoustic guitar players, you may put one to good use. I bought mine specifically for that purpose...that is its designated job. Your camera gives you more elbow room than mine does. I don't like shooting at super high ISO speeds, but if I had a 5DmkII it wouldn't bother me nearly as much.
Get the 24-70 and get a good feel for what you are doing. Shoot some performances with it. If you need a 50mm f/1.4, 85mm f/1.2, or whatever else...you will know who what where when how and why all by yourself.
Just because you have a super fast aperture doesn't mean you get to skimp on flash. Speed lights are awesome. You don't always add light because you HAVE to add light. More times than not you add light because it will improve the scene. You can create shadows, eliminate shadows, make the sky brighter, or all sorts of other tricks. It won't be urgent, but down the road you will want a 580exII or something similar.