two references to Mitsubishi's "promise module":
[Link: ce-pro.com][Link: ce-pro.com]My recollection is that they never "promised" a particular price for such an add-on module, which makes any such promise moot--easy enough to promise future compatibility if you can charge any price. Last price for the promise module, I think, was about $1k.
If you want to email me personally with your issue, I can probably hook you up with an appropriate Mitsu person, or dig up my old notes from their line shows.
Their Promise Module was a good idea for the time, when prices were so high and the technology so uncertian, but with prices dropping so fast, may as well buy a new TV.