Personally I think its about time that this is happening as Im an extended rearfacing convert
It is not known when it become mandatory but I have heard mid 2013. The car seat manufacteurs are already bringing out new seats that could accomadate this but most are stop gap type seats instead of decent extended rear facing. See carseat.se for the latest news from a baby show
Here are some bulletins and press releases on it
www.anec.eu/attachments/ANEC-PR-2012-PRL-017final.pdf
www.anec.eu/anec.asp?p=newsletter&ref=02-01
And here are some good resources for info on extended rearfacing (as well as carseat.se)
www.rearfacing.co.uk
www.facebook.com/#!/RearFacingTheWayForward?fref=ts
(please like the facebook page to get updates)