http://www.s8.org/gargoyles/askgreg/search.php?rid=815
That's Greg Wiesman's post from his "ask Greg" blog, stating that Sony is getting encouraged at SPECTACULAR SPIDER-MAN's rise in ratings lately on Disney XD, especially after the marathon. Season 2 episodes start in about two weeks, none of which have aired in North America yet. Others have posted this but that's the direct link to the source post.
Considering Sony wants SPIDER-MAN 4 on the big screen by 2011 and that animation can take a while, they will likely want to maintain Spider-Man's presence on the small screen. Rather than going through the motions of creating a new show from scratch, simply funding or getting Disney to fund a third season that already has a stable cast and crew (beyond whoever is doing other projects now) should seem cost effective. And hopefully a better option than just re-running 26 episodes for the next two years.