When I pre-ordered my N97 a little over a week ago, the expected ship date was in July. However, according to this post, Nokia notified North American distributors that June 2 is the estimated shipping date of the N97. Moreover, according to the official Nokia blog:
Pre-ordering will guarantee you are one of the first to receive the new N97. It will be shipped direct to your door from the production line so you’ll have it the same day it hits the stores in your country.
Now, although this is putting two and two together, it is putting an unofficial thing together with an official thing. Still, the June 2nd report seems reliable enough and I’m hopeful to see a nice package from Nokia on my doorstep around June 2nd.