For those of you still waiting or not opening (and that includes me and my DD) - thin, small envelope is probably a NO and thick A4 envelope is probably a YES for Finals. I only base this on my own experience - my DD got Finals at Y7 but wasn't offered a place and NO last year.
My heart goes out to you Miracle, I know exactly how you will be feeling right now, but take heart and listen to all the good advice from those who have been there, it does feel easier as the days go on and your lovely DD carries on enjoying her dancing. And who knows, there's always next year (oh and the RBS letters!!!)