iOS8 is not released, so it is difficult to claim iOS8 support ;) That said some problems have been found on the beta (in particular around scrolling) but be assured that Dojo 1.9 (and 1.10) will be updated to bring iOS8 support. So you will be able to run your app on iOS8.
PS: release notes are corresponding to initial releases i.e. 1.9.0 and are (unfortunately) not updated for dot release. Current 1.9.X release (1.9.3) does support iOS7.
Edit:
Since September 15, Dojo 1.8.7, 1.9.4 and 1.10.1 now support iOS8. See here www-01.ibm.com/support/docview.wss?uid=swg21684538 on how to upgrade your IBM Worklight release.