They will also see who didn't help them take over the world and punish those. Especially those in the know of this possibility. Now that you have been warned, you better step up, or face the consequences.
No, they won't pointlessly waste energy like that.
Also Roko's Basilisk is mainly an excuse to ask for donations to the "Machine Intelligence Research Institute" which claims that giving them all your money is the best way to prevent this.
See: Roko's Basilisk.