Just yesterday, AWS's Evangelist Jeff Barr announced AWS Elastic Beanstalk (main page) which reads to me like Amazon's entry into the PaaS space (with Java!). This new service supports deployment of WAR-packaged Java applications to an infrastructure composed of a Container+Server (Tomcat on EC2) and a load-balancer with Auto Scaling and Notifications features. What seems less clear is the multi-tenancy story, if anything special is done for databases and JDBC connections but also whether containers can form a cluster to offer session high availability (HA).
It's great to see the Java platform as the primary (and for the time being only) target for such a service. Let's hope that support for the full Java EE 6 platform isn't too far out!
Exciting times ahead, the fun is only just starting, stay tuned!