I don't think that the word "belief" requires that you continue to maintain it even if actual, solid evidence to the contrary appears. The whole point of "belief" is that it is performed in the absence of actual evidence.

I believe that the law of gravity applies universally. The fact that I would reverse that belief if presented with evidence to the contrary does not make me agnostic in my belief in gravity; it just makes me non-dogmatic in that I'll change my belief if the old one is provably wrong. After all, it would be unreasonable to continue believing something in the face of contradictory evidence.

But it's not unreasonable to believe something for which no evidence exists either way. And the fact that I would decide to start believing in a god should one be proven to me does not make my current beliefs in the lack of a god "agnostic"; it just means I'd act reasonably in modifying my opinions as needed.

"Atheism" does not require that I hold those beliefs forever and ever, no matter what evidence comes along later. It just means that, right now, I disbelieve in any god. And flemco's admittal that he'd believe in a god if evidence of one were presented to him does not change his current beliefs from "atheism" to "agnosticism".