A victory by the team seems 'within the realm of possibility'. [=a victory seems possible]
It's not 'beyond the realm of possibility' [=it's not impossible] that he will return.
new discoveries in the 'realm' of medicine
(..) No. I Promise. This is it. The Water of Sight. In every realm, there's a reflection. If the water spirits accept me, I can return to my dream, and find what I missed. The men who enter that water...the legends don't end well. A hacker who's faster than Ultron? He could be anywhere. (..)2015 Avengers: Age of Ultron