I'd like to see more and improved support in 8.0 for GWT. This means, to me:
Better support for creating a GWT project. Right now, unless I (and my co-workers have just missed something), when you create a new project with GWT support, it doesn't create the basic "standard" directory structure or anything else, and you have to resort to running the GWT command line tools. This isn't such a big deal (really, how often are you starting a new project), but also because it's so infrequent, it'd be great if I didn't have to remember the gyrations necessary to getting started.
As I'm still pretty new to the GWT world, these are the first things that come to mind. I'm sure that others can chime in more :)