Telepathic Illusions is quoted as "Psylocke can use Shape Change. If the character targeting her can't use Mind Control or Outwit or Perplex, she succeeds on a roll of 4-6." Does this mean that MC, Outwit, or Perplex have to be showing on the attacker's dial at that time or just that the attacker can use one of those powers at some point in its dial (and it may not be useable right at that moment)?

If a power isn't currently available in some way (on the dial, as a trait, via a resource, etc), then it can't be used.

And characters need to be able to use one (or more) of those three in order to prevent the 4-6 roll.