Since there is a separate tag for D&D 3.5 it would only include questions that pertain to pre 3.5 material. Questions for 3.5 material should be filed with the 3.5 tag.
The current consensus (always up for revisiting!) was developed here: Proposed tag synonyms for [dnd4.0] .
However, you might have noticed that very few questions are actually 3.0-specific. The idea at the time was that we should preclude the possibility that people would want to ask 3.0-specific questions. In practice, that hasn't really been a strong need yet. The logic still holds: people might want to ask 3.0-specific questions… but at some point, that allowance just becomes naïve. Having an umbrella tag might be useful. So, revisiting these assumptions is certainly possible.
One possible reorganisation would be to have this:
- dnd-3.x (for all of 3.x, maybe with dnd-3e as a synonym)
In practical terms, retagging a pile of questions of a sudden can be disruptive, so there's also that to weigh when considering changing things up.