It is quite possible to say there is no hope for Dortmund because I am also sure that Dortmund will not be able to score more goals in the second leg even though the match is held at their home ground. Because losing by four goals yesterday at Barcelona's home ground has made Dortmund's steps even harder to qualify for the next round in this season's Champions League and I am really not surprised by the result because Dortmund has not been good this season.
Very unlikely for Dortmund to make a comeback, 4 goals is a lot to recover from, it is clear that Barcelona are qualified for the semi final of the Champions League. Barcelona should worry less concerning the 2nd leg of the quarter final, the problem will be facing Inter in the semi finals, that match will be the toughest, tougher than the final, because both teams has their specialty, Barcelona with young talented players and Inter having rare experiences.
The semi final teams are already giving signs, each sides are making goals count for their advantage, next match will be for them defending their goals, and time to rest some important players.
Not only it is unlikely, it is impossible at this point. You wouldn't see a single bookie that would allow "which team goes next stage" type of game. Like there would not be any doubt in anyone's mind that Barcelona is going to next stage. However, the good thing about this is that we are seeing only the strong teams left and that will be a great deal for everyone of us.
Because when you have just strong teams facing each other, the odds are usually great and nobody gets low odds, that is always the most important one. Equal powers, it is not even about strong teams facing each other, two weak teams facing each other is also fine, look at Lyon vs United, close odds. That is why later stages are always fun, higher and better odds.