well eric kripke only had enough of the show written for five seasons and he wanted to end his storyline then... but coz the show is doing o well in america with ratings the show will most likly be going for a 6th season. p.s PLEASE SIGN OUR PETITION AND REPOST IT TO EVERYONE YOU KNOW!!! WE NEED SIGNATURES FAST http://www.gopetition.com.au/online/33184.html
I don't know if it is being cancelled, I hope not but Kripke did say that season five was the end of this STORY! not the series, he said in an interview that he could always start a new story and carry it on for a few more seasons. plus Jared and Jensen both have 6 year contracts so they would have to be involved if a new season was going ahead.
Actually, there might be a season six. It depends on Kripke, and if he wants to continue, and on the network. (if they want the show for another season) but both Jensen & Jared have said that they'd do a sixth season if asked :)
It's not being cancelled. It's just ending. Kripke has stated that he only had 5 seasons of story and that was it. And with where it is going this season, where could they honestly go? Both Ackles and Padalecki are tired of not being "home" and always on the road shooting. So, they aren't coming back.
There is talk of having a spin-off using the character "Bobby" as the series' star, but it's speculation at this point and would be up to the network.