It is not such a surprise.
It was a whole drama - if you recall it - what to do with 335i in US market: to add it to 325i & 330i, or to introduce the the 328i & 335i line-up. So, the initial decision was to move 3er coupe upmarket: introducing 328i & 335i, while sedan & touring would stay 325i & 330i till Spring 2007 when also facelifted 5er would come with same engines (and MB launching new C-class).
But the BMW NA have good arguments against: there would be a drop in sales since the customers would know 328i & 335i are coming to the sedan & touring sooner or later. Also the competition is strong enough (Lexus IS350 & Infiniti G35 both coming with over 300hp, not to mention upcoming C & A4) - so BMW should not stay behind.
What will happen to 5er sales remains a big question: now when 3er will have bigger I6 engines in the line-up. It could happen we will see an early 5er facelift launch - a few months earlier (January?) to save the sales.
So, the sedan & are getting 328i & 335i line-up a bit earlier - in October, just few weeks after the coupe launch. The PR release for new 3er sedan & touring engines (mind that Europe is getting additional 335i, 335d & 325d) will be issued around E93 PR: so late August /early September.