We are ment to be getting 3 737s this year - 300s but i dont think they can find decent aircraft.
I dont think the 757s will be replaced anytime soon, they are fairly cheap to run and bring in a fair bit of cash. personally i like the 757 and im a big airbus fan, i would like to see jet2 replace the 733 with 319 but cant see it happening anytime soon. they seem to be on to a good thing, so let um go for now. With jet2 thinking about going further afield and charter ops to the likes of SSH i dont think the A321 will be a good choice.