An earlier Troper hit it right on the nail. With internet gaming sites, blogs, and Youtube videos giving far more detailed and lengthly reviews than Xplay's 25 minute format could ever allow, it was only a matter of time before they would start losing relevance to their viewers. They haven't been making too many new episodes lately either - with only 3-4 shows per week, it's impossible to cover all the big news, releases, and relevant gaming info out there. And finally, watching them has become a waste of time, because they'd only focus on repeatedly previewing big-name titles such as Halo 4, Prototype, Darkstalkers, Medal of Honor Warfighter, etc while ignoring almost everything else on the market.
A personal theory as to why this happened is because companies like Activision and Microsoft would pay generously to promote their new titles, giving the show incentive to keep advertising them as a means to stay afloat... which sadly, probably backfired in their faces.
Would you believe I never fully watched the original Indiana Jones trilogy? I gotta correct that someday.