I know this subject has been discussed at length but I ran across this on the BMW UK website.
www.bmw.co.uk The new 5 series will have a 258 HP variety of the 272 HP N53 engine with High precision direct injectioin. The engine does not have valvetronic so we know it is the engine that run in the lean burn stratified charge mode. The intersesting thing is that it does not get quite as good as gas milage as the 272 HP version. It does however offer a 3 mpg improvement on the highway over the 328.
If I were betting man, this probalbly be the engine we will get. Not to close to the 335 horspower and still enough improvment over the 328.