While this might seem like a good idea at first, having a staging/qa environment that has the most up to date code is more important then having one that is essentially stable.
The reason this works is, in the work flow for test driven development, when a new feature is started the first thing that is created is your unit tests. This will create red lights on your CI server, and prevent your latest staging build from deploying for that day.

Why is this bad?

1. Delays an entire day of QA, working in larger teams this can become a problem.
2. Features that are not entirely yet coded, but have tests written for the entire of the features cannot have aspects of that feature that are finished hand QA’d.

Solution?
Very simple. Don’t require you’re QA server to have your tests pass. Leave that for your production environment.