You're right.
I wonder if TWC even makes the XL (or older) available to cable companies that want them. I hope that's not the case, and that only cable companies that still have an older Star are simply allowed to keep using them.
Maybe the only exception to the retirement rule that I can think of would be a very small cable company, such as a college dorm network or an apartment complex's private system if they choose to have a Star (such things do happen). But, otherwise, I think commercial networks should definitely be looking to upgrade. They're doing their customers a disservice.
Financially, I would agree they should be retired. IIRC, the IntelliStar is the cheapest STAR of them all and I think the XL is the most expensive of all of them, but the thing is most of the 4000's, Jrs, and XL's are serving small areas while the IntelliStar is intended to serve large urbanized areas. I do feel TWC should at least leave the LDL on for these older STARs on air to provide some sort of weather information in cases like Hurricane Irene and they chose not to show local forecasts, I don't see what's so difficult about showing text on screen live on air for the sake of their small audience until they reach a day that they chose not to support the older STARs anymore.