i dont really know what you mean about the ending of beowulf, but it wouldnt have been hinting a sequel. as it is they had to pretty much just make up the last half of the movie once the plot that is loosely based off the poem was over.
sometimes film makers just like to add some grey area to an ending to make the viewer think, or come to their own conclusions. prime example i can think of atm is with total recall (the arnie movie where he goes to mars, etc..). there are hints and dialogue that suggest that the whole event was just imagined and arnie isnt really there, he's back on earth at the rekall centre where he dies from complications with the memory implant.
personally i like this sort of thing, where something might not be completely black and white to the viewer. its more interesting and less predictable that way.
Quagmire: My fellow Americans, I have not been entirely truthful with you. I did gagoogidy that girl. I gashmoygadied her gaflavity with my googus. And I am sorry.