Ontem foi lançado o GWT 2.1 M1(versão recomendada apenas para testes), e nesta versão já dá para ver as novidades que vem por aí. No blog do GWT eles deram mais enfase a 2 novidades: A “MVP Framework” e o “Data Presentation Widgets”. Mas no meio das novidades menos destacadas, dá para ver mais algumas interessantes, como o suporte a BigDecimal e a java.logging.
E também falam o GWT terá suporte oficial ao Spring Roo, contando com colaboração oficial da VMware para isso. 
E no site da VMware tem uma notícia falando sobre essa colaboração também:
[quote]
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Spring, Google App Engine, and SpringSource Tool Suite
Google is announcing support for Spring Java apps on Google App Engine as part of a shared vision to make it easy to build, run, and manage applications for the cloud, and to do so in a way that makes the applications portable across clouds. Using the Eclipse-based SpringSource Tool Suite, developers can build Spring applications in a familiar and productive way and have the flexibility to choose to deploy their applications in their current private VMware vSphere environment, in VMware vCloud partner clouds, or directly to Google App Engine.
Spring Roo and Google Web Toolkit
VMware and Google are working together to combine the speed of development of Spring Roo, a next generation rapid application development tool, with the power of the Google Web Toolkit (GWT) to build rich browser apps. These GWT powered applications can leverage modern browser technologies such as AJAX and HTML5 to create the most compelling end user experience on both smart phones and computers.
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Fonte, links para downloads e etc…
Mais sobre a colaboração Google + VMware:
http://blog.springsource.com/2010/05/19/spring-google-appengine/
http://www.vmware.com/company/news/releases/vmware-google.html
http://code.google.com/intl/pt-BR/webtoolkit/business.html