When it comes to Newcastle there is a big potential in them to finish their group stage even as leader. Because we must have all watched how they demolished PSG not much time ago. 
Despite Milan's high dominance in San Siro Newcastle managed to resist them and get that one point also.
Truthfully I think the matches against Dortmund will also go really well for Newcastle. I think they can get at least 4 points.
I think Newcastle will lose only once in Group F and that will be against PSG away.
Newcastle has been really good with the champions league, they have really performed well enough to be able to qualify and they are definitely going to qualify for the round of 16, they used advantage they had over PSG to secure a win and lead the the group, the game against Dortmund will be really tough for Newcastle but then even if they loose they still gat a chance play in the next round. Despite Milan's high dominance in San Siro Newcastle managed to resist them and get that one point also.Truthfully I think the matches against Dortmund will also go really well for Newcastle. I think they can get at least 4 points.
I think Newcastle will lose only once in Group F and that will be against PSG away.
For me I personally think Newcastle and Dortmund are the team that will qualify in their group as they are the team with the highest points so far in their group PSG is still struggling but still have a chance with four more games to go, if they improve and try to get a win all four game they may most likely displace Newcastle to qualify for the next stage of the league, but wining Dortmund with their current form isn't looking possible, I hope they don't eventually crash out at the group stage.