If you work with ASP.NET and AJAX then you'll probably want to take a look at Microsoft's ASP.NET AJAX Roadmap document.
After restating their goal of "making ASP.NET Ajax the first-class choice for all Web 2.0 Developers" they start listing some of their ideas for the future.
Template driven binding sounds useful, and I've recently come across a few people mentioning that even though the version in Atlas had it's faults, that it was still a good idea. The DOM APIs around element selection look useful, and there are various other shiny things such as increased animation effects and data sources discussed.
The Ajax Control Toolkit is going to remain as a community project hosted on Codeplex, and they mention some of the ideas they have for new controls – my votes would go to Rich Text Editor, Upload, Grid and maybe Chart could be useful. I might have been tempted to add Progress Bar to that list, but Matt Berseth has a great control on his site that you should definately take a look at if you need that kind of functionality right now.
Finally some great ideas around tooling support and improvements. Script requirements profiling sounds like a valuable addition, especially when combined with the script combining feature that's headed our way in 3.5 SP1, and an inbuilt minify tool would be incredibly useful too (especially if it was scriptable as a build action).
I'm not really sure how many non ASP.NET developers will be embracing Microsoft's AJAX offering – I suspect there's too much of a mindset there to overcome. However for those of us using ASP.NET AJAX and the AJAX Control Toolkit there's a lot of cool things in the pipeline worth looking forward to.