I've worked in the cable business about a little over a year now, but more on the On-Demand side of things.
From what I've seen, we are unlikely to get any HD-only type package that would include something like HBO-HD, Showtime-HD, Discover-HD, HDNET.
There are some basic rules I've picked up on (someone else probably knows much more than I'll ever know):
1) HBO-HD is something HBO is most likely doing to increase the subscriber rate on traditional HBO. Same for Showtime. Five bucks is nice, but $12 is better....and we'll all pay the $12!
2) Showtime and HBO aren't necessarily in the business of promoting each others products. "Packaging" multiple premium services works for some subscribers, and it does get some people to buy more... but when you put $12 with another $12 you get a bunch more than $10 they'd have to split.
3) Cable Companies want to keep you from going to Satellite, and Satellite providers want you to drop cable...they do this by offering unique content...but the costs per subscriber (billing, customer support, subsidising the hardware, etc.) are enough that they need to recoup that in large monthly subscription fees.
4) Cable/Satellite is a monthly business. Packaging is an art-form. Mix some high-demand stuff with some low-demand stuff to make it all worth more to the consumer. ESPN with ESPN News, CNN and Bloomberg, MSNBC with CNBC...it works.
4a) HBO and Showtime Monthly packaging is an art form at its best. These guys know how to take a few HOT titles, package it with unique content and bundle it with a lot more lower-demand stuff and get us to pay for it all. We might only pay $5 for just the hot stuff, maybe a buck more for the unique stuff...and we'd likely not want the rest. But they stick it all together and charge us $12. And we gladly pay. Nobody is better at this than HBO. And Showtime is good at it too, but they just don't get the best titles, like HBO.
5) Billing systems are old. Real old. Mainframes with monochrome monitors. Anything that would complicate the billing process isn't high on anybody's list...especially if it doesn't help the bottom line. 'Cause it costs a bunch to make changes.
oh, and 6) There ain't much competition. Cable companies don't compete against one another, so you won't see one offering an ala carte deal when another is getting subscribers to buy the whole cake. Satellite guys get us because they have clearer picture, more channels, and HD! Why would they want to sell you a slice when the whole cake offer is all you can get from their competitors (cable)?
So, in my opinion, an HD package will never happen. And I don't like using the word "never."