The main thread for the new LUMIX G X VARIO 12-35mm/F2.8 ASPH./POWER O.I.S lens can be found here
and, being a Panasonic lens, I guess that's where the main discussion should continue but I thought I'd flag it up here in the Olympus section as well, not only because it's obviously compatible with m4/3rds offerings from Olympus but also because, as the lens is splash resistant, it is the natural complement to the Olympus OM-D E-M5 which is similarly weather resistant.
The extra cost over the E-M5's own weather resistant kit lens will, no doubt, be considerable but if only the best will do then the Vario 12-35mm f/2.8 must be a contender! Here's what the combo looks like, courtesy of 43 Rumors
My future lens choices just got more complicated!
I'll lock this thread and ask that any conversation continues here