Focusrite opened a page on its website where they detail the products that are compatible with the new Apple OS X Yosemite.
At the time we publish this news, Focusrite ensures that its Scarlett, Saffire 6 USB, Forte and Saffire Firewire audio interfaces, its Liquid 4Pre preamp, the Control 2802 as well as the Midnight, Scarlett and Liquid Channel plug-ins are compatible with OS X 10.10 Yosemite. Note that you’ll need to download and install Saffire Mix Control 3.5 with the Saffire Firewire interfaces.
However, the RedNet interfaces and VRM Box are not working with Yosemite. Focusrite adds that due to the complex changes brought by this new version of OS X, the VRM Box DSPs are not officially supported anymore with Yosemite. However, you can still use it as a headphone output with the Apple Core Audio driver on OS X 10.10.
Visit focusrite.com for full details.