I don't know why Megatron would stop project Predacon, when he can have both his regular army, the Vehicons and the Predacons with Predaking to take on the Autobots. They will be a real threat to both the Autobots and Humanity. Let's face it UM and WJ both had a hard time taking down Predaking
Because he feared Predaking might realize he's practically unstoppable and overthrow him with an army of Predacons.
I'm predicting the predacons lived the blast in the cyber matter. They're gonna break out and Predaking will discover the decepticon's plot to kill them. And then beast wars happen.
They were trying to prevent Terminator or the Matrix from happening, except it would have been machines uprising against machines.
Pretty much this. Megatron was so happy to have an army of beasts, but then the local one turned out to be intelligent, independent, capable of transforming and with great vision ("I gonna be the Predaking, like no Pred was before!"), and that pretty much soured Megs to the idea. If every Predacon turned out to be as intelligent/powerful as the King, then Megs would be pretty helpless to prevent a revolution. So the whole frame-the-Autobots plan went into play. Cool.
They ended up covering their tracks very well in regards to their plan, since Jackie and Magnus took the bait and blew the lab right to hell.