Firmware is never set in stone. Hardware is.. DLNA support could be added as soon as Sony works in the code into an update, same with MP3/MP4/AAC support. I would assume that like any project, they have a list of features on a board and then they go through and prioritize everything and hold back features deemed nonessential for a subsequent release. That's how we handle projects at my workplace anyway. Everyone wants everything now, but things don't work that way.
I think what most people want to hear is that DLNA or MP3 support is coming. I know I'd be happy with the former, and especially with a general timeframe.