I am convinced that the introduction of Premium Economy will have significant impact on the profit & loss statement. Especially on all routes with the A 380 where there is an *assumed* overcapacity of Y seats.
On that plane 84 seats of Y are replaced by 52 seats of Y+ thus requiring an average Y+ fare (with an assumed similiar load factor) which is approx. 61 % than the avarage Y fare with the same fare restrictions.
The already bookable fares for Y+ suggest that Lufty will reach this goal. ^
There is an additional effect: Taking out some capacity of standard Y will stop the immense pressure on special fares just to fill the large birds.
You indulge in the rosy view of a convert. A less subjective analysis has to consider the very real risk of cost-conscious passengers normally in business-class finding the Y+ product attractive enough for them to desert the J-class cabin. It won't take the loss of many of these to wipe out gains from Y-migration.
Of course, there might well be a queue waiting to take up any spare seats in business-class: there again ......