Without a trial, it is very difficult, if not impossible to dismiss PM.
Right now, you don't know whether PM lied or his children. See, the family has fought their case very cleverly. They have not contracted one lawyer for the whole family, they had three different lawyers for different family members. Each lawyer said that he doesn't know about the other client what the other's client said or presented, he was only representing his own client.
It is not established yet that PM lied on the floor of parliament (although we all know he lied, even the judges know). When Maryam's lawyer challenged the letters, and when Hassan's/ Hussain's lawyer presented Qatari letter (which was still unverified till the last day of hearing), they in fact told the court that either PM lied or his children is lying so judges had to start investigation.
The only person who has weakened their case is Chairman NAB who has paved the way of PMs suspension. Don't know why he did that, even PM's family doesn't know why he did that. Imagine if NAB chairman would say he was ready for an investigation, court would have no way other than referring the case to the right institution. This was the whole case of Shareef family's lawyers... to get the case referred to NAB and delay it till the day of judgement. Alas, it didn't work out well for them. NAB chairman ditched them when they wanted him more than ever...