Retrofit case studies exist (even for the 747). You'd expect them to exist, so this is in no way confirmation that a retrofit will happen or not. In one particular configuration on one particular aircraft, BA has come up trumps and lost no seats whatsoever. This is a result of rearranging wardrobes, toilets and other 'dead' space. For the rest there is a small loss of seats. However re-arranging other parts of cabin & other classes have minimised the loss. The new product is lighter, too.

One comment I've seen a lot here is that BA wants to maintain the density. You need to let go of that idea. Despite some seat losses BA will still achieve a higher density than all of it's competitors. Combine that with the fact that it's a more attractive product, and that the fleet isn't as fuel thirsty as it was in 2000 or 2006, BA think that there's a perfectly reasonable business case for it.

As for storage: the small 'table' next to the head of the seat is big enough for say, an phone (iPhone 6 Plus) and a wallet. The literature pocket at the top (there is also one further down the seat at the side), could be useful for hanging your glasses on.

I've seen nothing more regarding the IFE than the same Panasonic system being fitted to the 747. This may change as technology paces on.