According to Serebii.net and Pokemon.com, there is another event being available at local Toys R Us tomorrow until April 26th, but also on local wi-fi download starting on Monday to May 12th. The Secret Key item will open up a hidden door in the Galactic Building in Eterna City, which contains 5 household appliances. What do they do? If you obtain Rotom (you can get it this time before the National Dex, since it's part of the Sinnoh Dex in Platinum) and go to this room, clicking on one of the 5 appliances allows Rotom to enter the machine and change forme, while also obtaining a new move to that form.

http://www.serebii.net/platinum/wifievents.shtml

http://www.serebii.net/platinum/rotom.shtml

Meh. Rotom sucks too much to go through the effort.

Already online to everyone

Rotom is such a useless Pokemon. Give us Arceus instead!