Even though Heroes is at our near series lows with Adults 18-49 it is still one of NBCs better performing shows and its second best scripted drama, trailing only Law & Order: SVU.
At the current level, I cant see Heroes not being renewed. The ratings of course could continue to drop to the point where its a different story. But given the ratings carnage NBC has suffered, even if Heroes falls to the levels where Fringe currently is, I think its still a keeper. It could be retooled and re-launched perhaps, but a keeper nonetheless. It has strong international sales (though those will likely be weaker when attempting to sell an additional season) and still, relative to most shows very strong DVD sales. Those DVD sales are way, way down from season one, but still in the upper echelon of TV show DVDs. Of any show on NBC, only The Office surpasses Heroes DVD sales in the USA.
Especially with the ratings carnage NBC has suffered, I cant see NBC not at least trying to get one more season from the show. Again, thats based on the current ratings. In March, if Heroes is pulling a 1.5 adults 18-49 rating, thats a different story.