I would say 100% stay the way it is, even if it was double I would rather it stay the way it is. I don't have much problem booking rewards seats and even got a J-F on EK1 4 weeks out.

I don't think this would work for EK either as the busy routes where they can normally make a packet by selling the majority of premium seats, would then be taken up by 'reward seats' and the less premium routes left empty, where there is currently more 'reward seats' available.

I've only done reward upgrades from J-F, but Y to J must surely be easier?