You are right that next election won't be a walkover as PTI will be contenting against all parties and all those parties voter base will be out in full force unlike in by-elections.
PTI did what it could but reality is that provincial government holds all the power over development work in Karachi.
"get at least a few (3 or 4) very very important seats from Karachi." Lol dude, That's a arrogant analysis.PTI will lose this local bodies election because it's local leadership failed to create interest in it's voter base.That won't be the same during general election as people themselves will come out to vote.Who will they vote then?....JI will never win a national level election.MQM has no chance until Altaf returns.Karachi hates PPP.And, General election will also happen under PTI wave.PTI won't have any issue winning 15+ seats in Karachi in general election.