Yeah, continuity has been vague and has rarely come up in the series.
Which is why I'm taking Casino Royale as a prequel-of-sorts, despite the presence of Judi Dench, the modern setting and whatever other continuity problems there are. It doesn't matter.
Bond has been timeless and ageless to be able to continue through the years, so if you can accept that the 00 agent losing his wife in 1969 is the same guy getting hurt on the Millennium Dome, I don't think it takes much more a jump to just go along with a film where he gets his 00 in present day.
So, with the lack of a realistic timeline in the series already and with the folks behind CR always saying things along the lines of "it shows how he became the man in the existing films", it's a prequel to me.