Other IPTV service is essentially what Project Canvas is all about. For a glimpse of that sort of thing, take a look at recent Panasonic TVs and other AV gear with VieraCast built in; you don't get free choice, you get what's signed up to be on the platform. On VieraCast, there are things like YouTube, Tageschau, Eurosport, Bloomberg and the weather.
Project Canvas aims to be more open (so what you see won't depend on what brand of kit you have).
In-home streaming, if it were to come, would not be via the iPlayer functionality, but via DLNA compatibility, and I'd guess that would be most likely as a separate update. Also, remember that DLNA certification doesn't in itself guarantee media playback - the standard doesn't presently specify mandatory formats.
So, for example, some Sony sets are DLNA certified, but can only pay MPEG2 video; some Samsungs go the whole hog and support avi, mpeg, mp4, mkv and almost anything you can think of, with many variants of each. When you see the DLNA badge, it's best intepreted as meaning "Yes, it'll see your server. Now read the small print to see if it supports the media files you already have."
As for iPlayer functionality not being necessarily the sole preserve of the BBC, that's presumably because of the way it's being delivered. iPlayer is going to be an MHEG (red button) application on Freesat, where stuff behind the red button will be able to direct the box to connect to a stream on an appropriate server. So I don't suppose the update will actually be specific to iPlayer - it's more likely an update that enables the IPTV functionality of the MHEG engine in the box.
And so, if other channels were to add a red button application for their own catch up service (like 4OD or ITV Player), then those should work too, without any further updates.
Nigel.