Danny, after following your lengthy thread concerning cables, sales people, live sound stages, etc... I know you're serious about this stuff, and deserve a respnsible answer.
That answer: many broadcasters are sending out "digital" signals (DTV) already. And ALL TVs can receive and downsample ANYTHING that is out there, to regular NTSC. There's a big difference between the use of the terms "digital" and "high definition", as well as HDTV (High Definition TV), HDTV-ready, and so on. You've stumbled across the classic marketing game that you already know too well: obfuscate the issue, and the buyer will not beware.
I've even seen newspaper reports that say your TV will become obsolete. They're wrong: obsolescence will creep in through attrition, NOT through inability to receive signals.
I cannot find any good sites that describe the difference between DTV and HDTV. I'm sure you will spend some time now researching the issue, however.
Simple:
[Link: pbs.org]