You can rule Toby out because Marlene King said that Toby was the most honest person on the show. We know A lies a lot.
and about Mike...
TVLINE | Is there anyone we can officially rule out as being the evil “A”?
I can tell you from this season’s Episodes 7 and 8, there was a lot of speculation that Aria’s little brother Mike was “A.” But in the episode where Mike had an emotional scene with his sister, we did a direct cut right after that to Dr. Sullivan being watched, so it was like, ‘Oh shoot, we killed a theory!’ [Laughs]
My theory is that she'll come on to him...because he would be unbelievably stupid to betray Hanna's trust like that AGAIN.
Maybe the shots of them together are before she finds out? Or maybe she just forgives? I don't know. Either way, the relationship is just a subplot that means nothing to the bigger picture...but I just ship them so hard.