You may want to take a look at this latest update which refers to the preliminary "upgrade" and implies they are a long way off conversion to the new version:
"Note that you will not yet have access to the new SharePoint features or the new user interface. Rather, during this preparation phase, you will only see the new enhancements to the Office Web Apps as we previous communicated here. In addition, we’d like to reiterate Office 365 no longer supports Internet Explorer 7 (IE7)."