It's coming up sadly... I think it'll be the one after this one. Unless this one's being delayed because it'll be the last one, and they're making it Super Extra Amazingly Awesome like they promised. Either way, it'll be here soon. Anyone as sad as I am? DXP Weekend wasn't just great for the Experience points, it had some of the best game types on it. Reach may not continue it with all of the Daily Challenges and such.
I've seen a lot of people say that there won't be a need for it because of the challenges, but again, DXP Weekends had the best Game types, and with Bungie going to be busy with their next project... well who knows what'll happen.
Hopefully though, Reach will have some kind of "Fun Time" weekend thing, and continue they idea of a special game type for the weekend, and maybe even a Daily Challenge that has to do with it. Such as "Get an Overkill with the Chaingun on Power of Tower." Ah... wouldn't that be amazing?