Christ kids, calm down.
NCL will get two 737-800's and a 737-300 in replacement for two 757's - so no, there won't be any reduction in seats there will be an increase. The 737-300's will be used on routes such as ALC/PMI etc and the 737-800's more on the Tenerife and Turkey etc flights.
I've never heard such a load of rubbish about a more "luxurious product" the 737-300, 737-800 and 757 have identical cabins, the only difference is that the 757's don't have the newer style 737-800 lockers that have been fitted to the 737-300's. If anything, the product offering on Jet2 could actually be defined as more luxurious now, and the 737-800s are much quieter than the 733's or 757's and as Thomas Cook's fleet is a total mismatch and total luck of the draw if you get a horrendously crammed in 757 with massive bulky old seats or a new Airbus that has marginally more room.