Q1. Is their any solutions from Bitcointalk Forum team if any project not pay Bounty hunters after completing Bounty and successful?
Scam is not moderated on this forum.
19. Possible (or real) scams and Trust ratings are not moderated (to prevent moderation abuse).
Q2. Is it possible to take action against this type of project together?
The best you can do is to create a flag about the project, also leaving the project a negative trust will be fine. If other members see the flag valid, they will support it.
But know that the money not paid can not be pad agian, only the bounty manager can pay it and if not given, he will not be able to pay for it. That is why it is better to work with a bounty manager that has be escrowed funds to be paid for certain period of time.