I think we may see three levels of library technology development:
1 users and integrators: pull together end-user tools like Flickr, Furl etc. and merge them into library pages, implement but not extend frameworks and use toolkits
2 framework and toolkit builders: make easy technology interface layers to provide useful capabilities
3 infrastructure providers: provide Web Services or Web 2.0 APIs that can be used in frameworks and toolkits
The thing to be aware of is that above the infrastructure layer, you don't really need to know the details of how the underlying protocols are working. So I think one thing to do as a library technologist is decide at which layer(s) your organization has the interest, resources and technical capabilities to participate. If you're mainly working at the integration layer, for example, one role may be in requesting new features or new toolkits, to enhance your integration capabilities. Or you might write documentation for frameworks and toolkits.
That being said, I am most interested in the framework and infrastructure layers, so it is nice to see a presentation on Web Services at this year's Internet Librarian. Here's a presentation report I found from schwagbag - Internet Librarian :: Day 1 :: Web Services.