Adobe stopped updating the templates at CS3, and stopped shipping them at CS5, I think.
There's nothing magical about a template, though. All that command did was to open a File > Open... dialog and navigate to the directory where the pre-packaged templates were stored. You can still use those old ones, or any other template you have on your system by locating and opening the template file. The only difference between a template file and a document file is the file extension, which triggers templates to be opened as an untitled copy by default.
InDesignSecrets.com got permission from Adobe to distribute their templates (as Peter mentioned, created in an earlier version of InDesign). You can find them here:
This is still pretty annoying. Some of us actually make, and use our own templates. For example, I do tons of product mockups in my day to day and I have a series of basic templates laid out that I use for including the mock up image and the various specifications for each product. It's been super easy, in CS4, to choose file / new from template and just pop my template open. It was even nifty enough that Bridge would redirect to my templates folder for me.
Sure, I know I can still save my templates to another folder and use them as I always have, but the question is why would they just remove this? For all of the bloat that Adobe constantly adds on to this suite of applications, year after year, why on earth would they just remove a simple, useful, entirely unobtrusive feature such as file / new from template?