if you do not want to use JSF management and in Spring it not possible - no way RichFaces dropped that functionality because after it get implemented in standard it looks like just unnesessary duplication. And b.t.w. if even it be available why you can't allow JSF to manage the bean but decided to allow to do that RF? Just interesting where do you see problems with JSF.
P.S. Weld conversation scope solves that as well. and CDI in general could be used in order to manage your context dependencies in standard and easy manner.