I imagine that bt4 support is atleast planned on N9, not so sure if it gets in. The bluetooth.org page and the original N9/50 differences list hint that (it later got edited and mention of bt4 support was removed). But probably the software/driver support wouldn't be on the first release firmware anyway.
I wonder how a short time before they start manufacturing they need to have all the parts? If the bt4 support depends on the availability of TI WL1273L chip, then it can't be very long...