Well as far as OSS, someone can always write a driver from the community...
My handful of years of experience with FLOSS have taught me one thing: someone has to "be" the community!
I am not sure how you come to that conclusion, the update is in the driver software, not the firmware of the keyboard, so it's only up to whatever touchpad driver Linux or OS X uses. As far as BT is concerned, I would assume that the same driver is used, so it should work.
What I am sure about is that on Linux/OSX touchpad gestures will be the least of your problems, I rather was concerned about getting wireless to work
They don't use any touchpad driver at all but rather just use the "mouse emulation" mode of the touchpad. Yes, the firmware will convert two finger pan gestures into mouse wheel events, including horizontal mouse wheel events. And map two finger taps to right click button, and one finger tap to left button.
But not tap to drag.
The touchpad on the type/touch cover v2 seems to follow MS's "precision touchpad" protocol, which documents these two modes: mouse emulation and "touch screen mode". In the latter mode the touchpad will just report all the finger events. This is the mode that Windows 8.1 uses to escape the limitations of the mouse emulation protocol, and in order to enable the advanced gestures (e.g. zoom, right swipe for charms, etc.). Because it is a new protocol, different from Synaptics, no drivers exist for any platform other than Windows 8.1, so these platforms must for the time being use the touchpad in "mouse emulation".
As why it would not work when using the Bluetooth adapter, there is this quote from the
Surface touchpad gestures support page:
These gestures (open charms bar, zoom in/out, open last application) don’t work with Surface RT or if you are using the Surface Wireless Adapter for Typing Covers.
Surprise! If you've read the previous paragraph, you can easily figure out why they mention exactly this set of gestures: for some reason, they fall back to mouse emulation mode when using the Bluetooth adapter!
BTW, Wireless already works under Linux. It still does not work under OS X but because of the secrecy of Apple for everything involving 802.11 drivers I say it will
never work.