It's always been my contention that one box will, eventually, dominate in the living room.
The battle is currently being fought out between the set top boxes available from DirectTV/Sky/Dish/NTL/Telewest and other cable and satellite operators. They have the advantage of incumbency and the ability to integrate the backend service well with the front end. Perhaps Sky in the UK have done the best job to date with their Sky + box, but it has the disadvantage os till being a relatively dumb box - you can't store your music on it and you can't transfer programmes off it at the time of writing.
The IPTV market is failing to take hold in either the UK or the US, most incumbents such as Home Choice, Dave TV and Akimbo have suffered and changed business plan. Lack of incumbency is the problem facing anyone wanting to enter this market. However, there have been more successful examples in France and in the Far East.
The big gorilla on the block is Microsoft and their excellent Media Centre Edition (soon to become Vista). This can do everything and truly acts as the only box you need in the living room - you can telephone off it using Skype, can IM, store all of your music, listen to radio, record, view and transfer your TV programmes. The only real barrier I can see to Microsoft domination is their insistence on being proprietory.
A surprise winner might come from the direction of the main games consoles, PS3 and Xbox 360. However, I believe that these are likely to be the dominant entertainment centres in the bedroom rather than the living room.
The likelihood a couple of years from now of anyone having anything more than one box in any room to handle their entertainment is low. And they are more than likely to be networked over WiFi or BPL (broadband over powerlines), so that anything is accessible on any device.
The second battle is over the handheld device of choice - few people are prepared to carry an MP3 player, a mobile phone and a PDA (let alone a GSM system, a PVR and a remote for opening the garage door and setting the heating before you arrive home).
In all of this my biggest question mark is over Apple. Those of you who know me are aware that I am a great admirer of Steve Jobs. He manages to combine creativity and business nous in a way no one else can. With Apple's move towards Intel perhaps their proprietary devices (especially the iPod) will open out the great world and pose a real threat in both these markets.