Oh my, don't let HonzaP read it. It might be too much to endure for him. If you could just somehow reassure us that, at least, the Cube is fine...
Now, please, let me make you all bored with my interpretation of possible outcomes:
1. Eli noms Oskar, but that few liters of blood isn't enough to compensate her blod loss and heal her injuries, so they both die (then Zombie Oskar resurrects). It's the least plausible outcome of the four IMO, considering what miracles a little blood can do to her. (For instance the officer's blood donation provided her enough strenght to stick it out despite the nasty gun shot wounds.)
2. Eli drains Oskar; Oskar dies; Eli stays alive, alone again. Wether she goes on living her - without Oskar - pathetic life or puts an end to it, it's just wan and far too simple for a potent tragic end.
3. Eli refuses to drink Oskar's blood, Eli dies, Oskar remains untapped and alone. Now this one is really unsettling. Oskar becomes the killer of the only thing he really loves, and what is left for him in this world is worse than dying in a monster's embrace. Suicide, as soon as possible, is the only 'solution'. The cramp of the hangman's noose would really be just a tender stroke compared to the stranglehold of the grief that the loss of Eli would call forth.
4. Eli should have died an instant and probably kind of showy death if Oskar had hit her heart with the blade, so this must be just a 'casual' injury - altough not a minor one -; remeber what tricks she has done with that broken broom. However, this little impulse from Oskar made the real Eli resurface. Drinking a liter or two of Oskar's blood could save her life, so in the end we would have Eli alive, Oskar turned, and both of them predestined for a 'happy', mutual future in eternity. I find this one the most likely. At least, this is what I would like to happen.Edit: Darn, I'd chop my nonexistent hamster's left nut for a 15th chapter that sorts out all the misery. This downbeat ambiguity kills me.