Whilst being vague about exactly what's going on, the devs have an in-game event planned beginning 11am EDT on April 28th. Apparently 'all CHAOS is going to break loose' until 12am on the 29th. There's the promise of merits, badges and lovely XP. Also at 8pm EDT, there will be a special address from Lead Developer Positron; apparently he has some info to share. What could that be I wonder? The broadcast will also appear shortly after on the game's official website.
Also keen to bring heroes and villains out of retirement, anyone who logs on between 28th April and 3rd May with an expired trial or retail account will be able to access the live servers and join in on the fun. As a final incentive, any character -- that's character not account -- who logs in between 11am on 28th April until 31st of May will find themselves awarded with a special fifth anniversary badge.
There will also be some cool contests running, including one where you get to design a t-shirt logo and another where you can create an homage video. Details will appear on the official site next week, but for now, more details can be found here.