I wouldn't bother with this. I guess some screen protector manufacturers (sg. bestskinsever) will wait for the official product are launched before releasing their protectors... It's the best way to ensure a great fit.
I'd say look after you rphone for a week and get a protector that you know fits, after the iPhone 6 launches.
Still looking for a good glass screen protector that will he here by the 18th. Would love any advice or recommendations! Zagg doesn't look like it would arrive on time.