Perhaps the more likely interpretation is that the negotiations to acquire B763s have broken down. Worldwide there are only 7 B763(ER)s up for grabs, that are about 15 years old and only four of these are likely to have a seat configuration that may be attractive to an LCC such as JET2. Doubtless the conditions/price offer to JET2 was unsatisfactory, so they walked away but doubt that the future long haul plans have been shelved for the forseeable future.
One other possible source of B763(ER)s might be from Thomson, who recently furloughed 137 pilots and that equates to a large number of planes sitting on the ground. So far they have only reduced their fleet by 1 x A321. Their fleet includes 13 B763(ER)s.