Here is the final word from the TCM Programming Department in response to my question about their HD Content posted during a "People Behind the Network Forum" held at 15.30 hours, PDT, at the Hollywood Roosevelt Hotel on Friday afternoon, 23 April, 2010:
TCM currently up-converts all content on the HD feed at this time and will begin to feed actual HD content to the HD feed within the year. Their initial objective was to get the HD feed in place and then, as they can acquire HD prints from the studios; HD prints for the licensed content which they own outright, and HD prints for future programming; begin to feed HD and down-convert for the SD feed.
The reason for the long lead time is that some of the rights to the films are negotiated as far as three years out. While normal programming is done between 5 and 7 months out - they are currently programming general content for September / October 2010 - special circumstances, such as significant dates in history, director or actor's birthdays, or other events can require planning as much as five years in advance.