Some of the new 1H2012 LEGO Technic sets, have been reported to ship with a redesigned version of the "Technic, Liftarm Triangle Thin" (2905) part.
New mold number is 99773.
Most likely the new design will replace the old one, rather then both co-existing in the future. This because the same new set (9390 Mini Tow Truck) was received by different persons with the old and new versions of the same part. So most likely the old version is already being phased-out, with TLG warehouse exhausting their stocks and whatever you get just depends on the date your set was packaged.
Although the old design is still the one listed in the partslist at the end of the instruction booklets. Some photos we start to see around also show the old design. It is for instance the case of the yellow ones at the 9391 Mini Crane.
Ont the other hand "old" sets like 8070 Supercar, from the 1H2011, is now already being shipped with the new version (I'm building two of them right now).
It is my conviction that this new designed was motivated to allow the possibility to use any other parts, adjacent to the liftarm axle-holes where the triangle extended before.
The new design might look a bit weird now that we are used to the old one, but guess soon no one will think about it anymore.