InfoQ: How do you think this development will affect RIAs? Do you think that it will open the road to even richer applications? What would those look like?
InfoQ: Dion Almaer wonders on Twitter, "How hard will it be to debug code via Firebug once you are in JIT'd code?". What do you think about that?
Honestly, it won't be that different (to the frontend web developer, that is). Most of the changes are taking place far underneath the core of the engine, making the end result quite seamless to most web users.
InfoQ: Do you see other vendors following the example of Mozilla, with just-in-time native code compilation?
Sure thing. A lot it depends on the details of how other ECMAScript engines are implemented. I fully expect to see other engines making improvements similar to what was done with Tracemonkey.
InfoQ: Besides TraceMonkey what other breakthrough should we be expecting in the area of client-side scripting in the near future?
The next big thing is going to be threading. There is the Web Worker proposal being worked on by Google, Apple, and Mozilla under the auspices of the W3C. We'll start to see this arrive in browsers quite soon (some form will be in Firefox 3.1) and it'll absolutely help to revolutionize what's traditionally possible in a web application.
Expect to see more of these improvements make it in to browsers in the upcoming years.