This is against the grain, but it is obvious to me that the way forward for web development is to rise above Javascript and simple DOM mangling, which is what most of these popular tools assist with. Javascript does not scale complexity and manipulating DOM elements directly is both error-prone and a lousy programming paradigm.
We need something in between that offers a sane development model and deals with the complexity and anachronism of the underlying platform. GWT cross-compilation is an excellent example. It has enabled the painless development of complex Javascript-based web UIs[1], with the tool support of any other software development project. This is what I'm going to look to for the future of web application development, not patchy solutions to the complete mess that is barebones Javascript development.
For examples of what I have done with GWT: TeampostgreSQL (http://www.teampostgresql.com), a rich PostgreSQL web interface, and my HTML5 game engine (http://www.webworks.dk/enginetest).
EDIT: By the way, it is only a matter of time until we have complete canvas-based UI libraries, frameworks and tools suites akin to Flex (probably from Adobe, too). When that happens the web will really have arrived as a rich client platform. I would be very surprised if there isn't a few projects in this space nearing completion at this point, since the underlying technology is basically ready.