It's not Ableton Live 9, but version 8.4 of the hugely popular DAW, which has been introduced in beta today, does address one of the big limitations of its predecessor by offering native 64-bit support.
In a nutshell, this means that Live can now access much more RAM. With the 32-bit version, you're limited to 4GB, but the 64-bit edition raises the bar to a theoretical maximum of 16 exabytes (way more than you have installed, we think you'll find).
This means that you can work with Live Sets that are much larger and more memory-intensive than before, while there's also support for 64-bit plug-ins and 64-bit ReWire configurations.
On the downside, the 64-bit version of Live 8 will not currently support Max for Live, video, or The Bridge.
Ableton Live 8.4 will be a free update for registered Live 8, Suite 8, Live Intro or Live Lite 8 users, and these same users can download an Ableton Live 8.4 beta now.