Flying on a 757 would be hell and it doesn't go in line with Thomson's long haul standards what have been set very high since the 787 was introduced. I would expect that they will offer the Dubai cruise charter from more UK airports such as EDI and EMA in W17 if it proves a hit in W16 but if they were going to offer more flights, that would mean they might have to base a larger cruise ship in Dubai in W17 or base 2 cruise ships in Dubai in W17 what is very unlikely due to lack of ships.
I think the Dubai cruise charter 787 flights have been made possible due to lots of 787's being free in W17 because the 787-9 gets introduced. I would expect that they might announce more long haul routes next month to fill the 787 schedules so they aren't just parked on the ground all winter. They have the huge masterplan on what destinations they want to fly too so we might see one or two of them announced and hopefully they won't just be LGW only routes. I hope they do a duel launch like they did with Puerto Vallarta in 2014.