City are once again eliminated from the Carabao cup, Pep already said before the game that he would not be prioritizing the Carabao cup this season, because they have such a small squad and many injuries. I watched the match and City didn't play too badly, but they struggled to create chances. Now they can fully concentrate on defending the three titles they won last season, this weekend they face Wolves and in mid-week they travel to play RB Leipzig in the CL, and their next game after that is Arsenal, if City can win all three matches, they'll quickly forget about this defeat from Newcastle tonight.
But I think that Newcastle will forget this victory not so soon for a number of reasons 
On the one hand, Pep Guardiola has really more important goals to win titles this season. On the other hand, this victory over Manchester City is very important for Newcastle United and Eddie Howe to raise their spirits and gain confidence in their abilities, because Newcastle did not start the championship too well with 3 wins and 3 defeats to their credit, unlike their opponent, who had shown an absolute result before. Also, let's not forget the terrifying statistics for Newcastle in matches with City before when in the last 10 matches the team lost 8 times without winning once. Therefore, this victory can help Newcastle get on the path of permanent victories.