Ok, this happened, chromium-browser was removed from testing and will not be included in Debian squeeze.
Some days ago (before the hard freeze) I contacted the release team and asked about a possible inclusion of Chromium 6 in squeeze. The main reason of this request is that in April there was at least one major refactoring of the SVG code (webkit). The internal webkit copy is too outdated in chromium 5, and backporting any future SVG security patches (and unfortunately the story says they are frequent) is very hard.
I got no answer, and after one week of silence and the hard freeze announcement, I realized that chromium 5 is not supportable and decided to upload chromium 6 in unstable (It was already in experimental). I asked the Release Team to unblock chromium-browser 6.0.472.53~r57914-3 or remove chromium-browser 5.0.375.127~r55887-1 from testing.
Well, after one hour they removed chromium-browser from testing.
I failed, my efforts to get chromium in Squeeze were in vain. Debian failed, a modern and very appreciated web browser will not be included in our next stable release.
Update: The relase team unblocked chromium, squeeze will have chromium!