NI were controversially beaten 1-0 by Switzerland at Windsor Park in the first leg of their World Cup playoff, and head to Basel to try to overturn the deficit in the second leg on Sunday.
However, if O'Neill fails to lead his nation to their first World Cup since 1986, Dowie feels that the former Shamrock Rovers manager would not be short of offers to go elsewhere.
"No-one's 'unsackable', but if anyone can be, Michael is," Dowie told Sky Sports News.
"On the other hand, I do think there are other opportunities. He will think 'who we've got coming through, and can this group of players replicate that again?'
O'Neill has been in charge of his country since 2011 and led them to the last 16 of Euro 2016.