Whilst Amy Rose may not be a Sonic Character that debuted in the Dreamcast Era which the 3rd Live Action Sonic film is to take cues from, she might have some potential in appearing in it. Overall I don't really expect Shadow the Hedgehog to be the only familiar Sonic character to be seen in live action form for the first time come then, Rouge the Bat might also appear, if she does then she should be voiced by a Famous Singer/Fashion Icon. As for who could voice Amy meanwhile, my bets are currently on Sarah Silverman or Kate Micucci, which is what the initials based on the character limit with Change.org Petition titles stand for. Why I say them is because of what they sound like in a way that would be pretty fitting for Amy, plus the latter has actually worked with Sonic's voice actor in live action form a fair amount of times.