RIM has already spelled out in the developer documentation and roadmap that BlackBerry 10 will have Bluetooth 4.0 but its nice to have more confirmation. Bla1ze noticed that a BlackBerry 10 device labeled "RFH121LW" has received official Bluetooth 4.0 certification from the Bluetooth SIG. The OS it was running for the test is a bit old at v10.0.9.341 which is older than the current Dev Alpha beta and the internal builds.
Let us know if you spot more details!