Folks, they're not going to update the 135mm f/2 SF just so that it can compete with the current 135mm f/2 L.
I assume you're talking about the 135 f/2.8SF, an old design with film era relevance which will probably quietly disappear from Canon's inventory sometime soon. I wonder how many they sell per year? It's the venerable 135 f/2L which also hales from last century, April 1996 to be exact which I'm hoping to see upgraded.
I stand corrected: The 135mm "Soft Focus" lens is an f/2.8. My point is that there were some calls on here to upgrade that lens, and I just don't see it happening. Personally I'd like to see the 135mm f/2 L get upgraded AFTER I buy this current version. A new one will undoubtedly be out of my price range.