implication_next_cycle = {{SIG0} |=> {SIG0}}

This assertion looks very similar to the previous one, but the implication operator |-> has been replaced by the implication_next_cycle operator |=>. So this assertion is equivalent to: {{SIG0} |-> {true;SIG0}}. It checks that if SIG0 is true in the current cycle, it should be true in the next clock cycle. So if SIG0 is false at the start of a match attempt, that match attempt succeeds immediately. If SIG0 is true during the start of a match attempt, the match will succeed if SIG0 is true during the next cycle, or fail if SIG0 is false during the next cycle. Compare this to the operation of the earlier assertion {SIG0;SIG0} which  fails when SIG0 is not true at the beginning of a match attempt.