Yes, the episode is actually happening.
The hour long special episode, called "The Simpsons Guy" (see what they did there), will see Bart skateboarding with Stewie, Peter and Homer fighting after arguing whether Springfield's Duff beer or Quahog's Pawtucket is better, and Marge and Lois bonding together.
A sneak peak was give at Fox's Upfront presentation.
Several stills from the presentation leaked on to the internet shortly afterwards. However a rep for Fox told BuzzFeed that "though some photos leaked from Fox's 2014 upfront presentation on Monday, an official look won't be available for at least another month".