I've heard from different sources (k123 and some marketing guys at Nokia Germany) that the consumer device will be released in September.
Accordingly to Nokias new strategy "announce late, release early" I can't imagine the consumer device will be revealed tomorrow. I could be wrong, though, as some developers with access to the consumer device told me, that they would be greatly surprised if it will be released as late as September. They're counting with June/July.
Also I was told that the dev device will be announced and distributed well before the consumer device.

My bet is, that the dev device will be announced tomorrow (tech demonstration and so on) but with the clear statement that this is not the yet to be announced consumer Harmattan device. The consumer device will be announced in the beginning of September and will be available in stores one or two weeks later.