I would assume that the press and industry officials would already know to bring their 3DS's to the Nintendo conference and that Nintendo might have mentioned that to them in their conference invite.
And it would make sense for them to bring it with them because that is the only way to portray the 3D to the audience without handing them all a pair of 3D glasses, and since Nintendo's big thing is 3D w/o glasses....
Either way, I just thought it would be a good idea to advertise a 3DS update during the Nintendo 3D conference as a way to not only get everyone to update their 3DS, but to tune into the conference and be aware of whats coming up for Wii, 3DS & Nintendo in general (Cafe).