IBM's Service Component Architecture (SCA) is a cracking new solution to the issue of "what represents the service", a definate improvement over WS only technologies it starts from the basis of assuming that the container at invocation should be standardised, but that the implementation and container at the produce can be variable. This really helps from a conceptual and logical architecture perspective as it gives a level of consistency that WSDL, and even WS-IF struggled with. Most interestingly around SCA are the companies who have said that are going to adopt it. BEA, IBM, Oracle, SAP, IONA, Siebel and Sybase, now while the idea of SCA is not Java only, pretty much all of this camp is in the Java world, I guess its like how JCA isn't Java only as it connects to lots of external applications, it just "happens" to run in Java. Definately worth a look and something that I'd expect to gain rapid adoption. Its already in the wild in IBM's new Process Server and their Integration Developer.
SCA is in someways an extension of the work that BEA did with Beehive so I'd expect them to be able to move relatively quickly, as should Oracle as they are moving from a similar technique using WS-IF, which IBM used in the previous version of their product too.
Strong technology with a very devent future.