Apparently Nokia will ship a phone with Harmattan before Intel ships their tablet. Now here is why the questions dude, so please chill:
Harmatten was/is the next step for Maemo but Harmattan has been re-branded a MeeGo OS.

However, a device running Harmattan will not be a fully realized MeeGo device as it will not yet have all of MeeGo components. Think of it as having MeeGo 0.9 and the Intel device as having MeeGo 1.0 (version numbers used as an example and are not fact ).

So with a tight interpretation of your question: When does Nokia/Intel plan to release the first devices pre-installed with MeeGo? ..the answer would remain: The announced Intel device.
A loose interpretation of the question and the answer could be:
Nokia's planned Harmattan/MeeGo device.

If you take out the word pre-installed and loosely interpret the question, the answer could be: It already has, the N900.

Now I'm no expert here but that is what I believe based on what I've read. The reality could be something all together different as I have been known to alter my mental state through the use of chemicals and natural herbs from time to time.