"역시" has a veriety of meanings. First of all, it means "also" or "too" Second, it means "still" Third, it means "after all" but we often use "역시" in a sentence such as, "(역시) 그럴줄 알았어", which means "I knew it" "(역시) 네가 해낼줄 알았어", which means " I knew it you could make it." Meanwhile, "혹시" is used for the meaning of "probably", "presumably" etc... ^^