Coming from a 2009 Macbook Pro

Well I use my MacBook Air for running Parallels with Windows 7, I've used Final Cut on it (though I wasn't doing any large projects) and had no problems with it and I'm using the basic MBA.

As for the HD 4000, I've been very impressed with it. I can play things like WoW, Left 4 Dead 2 , Portal 2, Diablo 3, ARMA 2: Day Z, Borderlands 1, all with about medium graphics settings and they run pretty well. For integrated Intel graphics on an 11" Ultrabook I really can't complain.

I don't know about the other stuff but if you're talking about Logic Pro for music, then that runs just fine and I have the latest MBA standard model, with nothing special. I would imagine with stuff like editing movies the processor would be fine, but you might run into issues with storage space if you are trying to upload an entire video to edit and cut down.

The 2012 MacBook Air should be a pretty good bump from your 2009 MacBook Pro. My mother has a similar model to yours (that I recently upgraded to an SSD), and my 2012 MacBook Air was noticeably faster at processing photos, opening large PDFs, etc. (I say "was" since I lost the MacBook Air and replaced it with a 13" rMBP). I run Windows 7 in a Parallels Desktop virtual machine, and the Air ran it well enough (even the 4GB model, but I'd recommend 8GB).

You might consider the 13" rMBP as the Air's display isn't quite as good as the ones on the MacBook Pros. In particular the color gamut is much better on the Pro. Or if you can hold off a few months the Haswell updates should provide a significant boost to graphics performance if that's what you are concerned about. Consider replacing the hard drive in your 2009 with an SSD in the meantime, as it should provide a significant boost in startup times. It will also help with the virtual machines, since with 4GB in your Pro I'm guessing the virtual machines page out to disk a lot.