According to the latest stats at http://www.bitcoinwatch.com, the market value of all bitcoins currently in existence is just under $100 million; so, trading volume of $1 million per day means that around 1% of Bitcoin's entire float turns over every day, around 30% of the float turns over every month, and the entire float turns over about once every three to four months. That's more liquid than a lot of publicly traded stocks with similar float.
PS. moonchrome, I'm not sure how your comment relates to my post, which is about trends over the long run ("many years or even decades"). Why are you responding with a comment about current trading volumes?