I think you are right there Sooper. I can't find on Canon USA's website a 5 stop IS system. There is tons of forum threads that their newest IS is 4-5 stop IS. Some Canon websites claim 5 stop and I have heard it many places. I think the newest lenses that some claim are 5 stop are the 70-200 f4 and the 200mm f2. Here is a quote from Canons euro website:
The EF 200mm f/2L IS USM is a high-performance medium telephoto lens for professionals. Its large f/2 aperture ensures optimum results indoors and in low light situations.
Features
L-series construction
Large f/2 aperture
5-stop Image Stabilizer with tripod detection
Super Spectra lens coatings
Fluorite and UD lens elements
Ring USM auto focus with full-time manual focus