The date has been oscillating between late 2012 and early 2013 in recent reports, by the way, even from the same sources, not sure whats more accurate.
I don't have a reference, but i remember reading somewhere that Chang'e-2 was essentially built as a spare for Chang'e-1 and once the first once flew successfully, received it's pre-planned upgrades.If they learned anything from their success there, and from the early days of exploration technology developments, back when series numbers for probes in double digits were not uncommon, one would hope that they are building spare(s).
From Xinhua, China starts manufacturing third lunar probe.
I wonder whether the Chinese will have any "repeat capacity" in the Chang'e programme.
Mission to bring back lunar soil By Xin Dingding (China Daily) At: http://europe.chinadaily.com.cn/china/2012-03/16/content_14845488.htm
Using Lunar orbit rendezvous (LOR) greatly increases the mass returned to Earth, a few hundred grams for the Russian Luna sample return missions compared to two kg for LOR. This is because you do not need to carry the 1 km/s of return propellant from Lunar orbit all the way down and back up again (a 4 km/s penalty).Using Lunar orbit for the return also allows return from any point on the Moon. If using a single burn direct ascent like the Luna missions, you are restricted to certain areas of the Moon, I believe to be in the Eastern hemisphere.
I thought, that doing lunar orbit automatic docking in sample return missions could mean also technology test, which can be greatly needed for manned missions. Don't know exactly why , but for me may be useful for precise testing of spacecraft and landing before actual human flight, or for orbital maneuvers without human presence like for constructing orbital station.
Docking tests with crews can be done in LEO, which is why I linked this approach to possibly technology-testing for a Mars mission.But I still don't see why they would want to complicate and already-complex mission which only the Soviet Union has previously accomplished.