It makes sense from a manufacturing PoV to only produce one box. less costs, easier to organise from a logistics PoV too. As the Sky+ service is free there's no real need to differentiate between the boxes either. it also means that if someone then decides to buy a HDTV then the box is there and bingo, an instant, extra £10 per month if the customer goes for it.
The story about the £10 HD sub being dropped? I can't see it TBH. Yes the channels available are changing to a 'linear' subscription. Previously it didn;t matter what package you had, if you added the HD sub you got all the HD channels (Sports, movies and ESPN excepted) as well. For example if you didn't have Knowledge you still got Discovery HD, Nat Geo HD Etc. From October you'll only get the HD channels that mirror your current subscription. In other words no knowledge pack, no Nat geo, Discovery etc. No news and events, no Eurosport, Rush or SSN HD.
If it's correct that Sky now have 3 million HD Subscribers Sky would be stark raving bonkers to pull the plug on £30 MILLION pounds a month. £360 million a year isn't pocket change! Find some way to make that up and yes, they'll consider it. Personally it'll be next year, maybe even 2012 by the time the HD sub is dropped.