I am currently looking a lot into git-flow, and trying to figure out, how to use it for the projects I am involved on.
I have looked at the various git-flow tutorial
I realize this is an old question, but I just found a fairly simple way of handling it on my end.
On my development server I basically have two working copies, one for v1.0 and another for v2.0.
I then create a separate "develop" branch for v2.0, and when I run "git flow init" on the 2.0 environment, I use this as my "next release" branch.
I am sure you could do the same for the master branch, but for my purposes this was sufficient.