However, even if Roku were willing to further enhance the firmware of the SoundBridge, support for WMA 10 Pro presumably could not be added as there is no decoder available for the Blackfin processor used in the SoundBridges. The same applies to FLAC.
I am sorry to correct you - but since FLAC is open source, they could have added it at any time if they wanted (Reciva did this in 2007, initially for Roberts). The reality, I assume, is that the benefit to Roku in terms of new sales was less than the effort of integrating the algorithm, and perhaps that there was insufficient space in the Flash memory (especially in some of the older SoundBridge units).
Either way - you are right to say that none of this seems likely to happen now. Which is a real shame, and a source of continued frustration for all of us.