See the discussion at #15873: As noted there, Spring Framework 4.0 supports AspectJ 1.7 as well as 1.8 M1. We need the latter for building the framework on JDK 8 - however, at runtime, the choice is up to you.
That said, we have a few explicit dependencies on AspectJ that we're exporting in our POMs. Maybe we need to reconsider what we do for the time being, until AspectJ 1.8 is final (which it won't be before Q2 2014).
We're xposing AspectJ 1.7.4 to the public now, only using AspectJ 1.8.0.M1 for ajc in our build. This should be a fine compromise for the time being, since AspectJ 1.7.4 works fine with JDK 8 as well - for all the purposes that users need our declared dependencies for (i.e. pointcut evaluation and load-time weaving). If somebody wants to use ajc in their own build, they'll have to declare a specific AspectJ version for that task in their custom build anyway.