Are features from Blender daily builds typically in next release?

I have a script which is not working on Blender 2.69, but it works fine on the latest build from builder.blender.org/download. Perhaps they tweaked something in how rigid body simulations are baked to keyframes.

Should I expect my script to work with the next Blender release?

In other words, do the daily builds have experimental features which will be removed or is it typically just features that are planned to be included with the next release?

There's a Variation column on the builder download page, if it's Official, then it's build straight from current master branch.