In an official announcement on its web site, gamer channel G4 told fans that its two of its most popular and long-running shows would end at the end of the year:

G4's two longest-running and defining series, Attack of the Show! and X-Play, will be ending their run at the end of 2012. Both shows will include original episodes through the end of the year, and will look back at their most memorable moments as we lead up to their final episodes.
Both long-running shows helped define, as well as expand, the pop culture and gaming TV experience for a generation. We hope you've had as much fun watching them as we have had making them...

As a send-off, both shows will feature a lineup of famous guest hosts, including John Barrowman, Horatio Sanz, Michael Ian Black, and Paul Scheer. A complete list wasn't provided, but don't be surprised if some G4 alumni -- like Nerdist's Chris Hardwick, Kevin Pereira, and Olivia Munn -- show up to be a part of the extended farewell.

(via G4TV)