First off, as said, the timing chain is still located at the back of the engine. The N47D20 is still being used today. I have not read anything about them changing out the engine, though there was this article from 2012 about BMW doubling down on their use of the chain at the rear of the engine, supposedly to go into production cars this year (2014), but I've not read where they've actually started using the engines. These newer engines are supposed to share many of the same components, have the same amount of displacement per cylinder (whether gas or diesel), and use the same mounting points in the engine bay. Even the HP ratings would be about equal per cylinder (though different between gas/diesel for obvious reasons). Until they do start utilizing the new engine, BMW continues to use the N47 as a mainstay in their fleet.
Since BMW will not own up to the timing chain problem (publicly), the best we can do is to see what the BMW owners community has said about it. According to the community, the problem lies with the crank shaft sprocket. This is an excerpt from this forum:
BMW recognized it as a fault and fixed the sprocket issue in roughly March 2008 (some older engines were still installed at a later date) but later model have since failed, the mechanics on the site have seen mainly jumped chains on manual cars that have been been ragged, auto's don't do the same harsh gear changes and so are less prone to failure.
Still, others claim the manual tranny v. automatic theory does not hold true. Failure rate does seem to have decreased dramatically since BMW made the changes, but that does not mean you won't have mechanical chain failure on the N47. Bottom line, if you start hearing the timing chain start rattling, you should get it looked at.