Exactly. Design patterns are a type of language... in fact Christopher Alexander, the architect who came up with the concept, talks about "pattern languages" (and that's the title of his first book). And category theory is a language... it's a language much more suitable for talking about the kinds of abstractions we have to deal with in software engineering (and maybe mathematics or at least parts of mathematics as well). Design patterns help, but they're too fuzzy... category theory lets you say the same things much more precisely.
I like this comparison, because one of Christopher Alexander's requirements for patterns is that you can draw a picture of them. And what is category theory but diagrams!
