Assuming a based B788..... I'm going for the easy option and copying the schedule for this years TOM B788 based at BHX which operates 6x flights a week:
Cancun x2 weekly
Punta Cana x2 weekly
Orlando Sanford x1 weekly
Montego Bay x1 weekly
.... but maybe Punta Cana 1x weekly and Orlando 2x weekly?
Some posters have suggested Goa, Phuket, etc, however if TOM are to base a B788, it will almost certainly do just westbound flights during the summer. This is becuase all westbound flights leave the UK in the morning, and arrive back early the next morning. However an eastbound flight wouldn't leave until the evening, and would not arrive back until the following evening, during which time you could have operated two westbound flights (hope that makes sense). Therefore you only find TOM doing eastbound flights from the bigger bases (LGW, MAN) during the summer where there are more aircraft based to utilise.
I also wanted to take a look at which long haul destinations TOM are offering from LGW this summer. This might give some hints also as to what the new BRS destinations might be? Here's the list below:
LGW - Summer 2017 LongHaul:
USA
Orlando Sanford - 2x weekly B789
Mexico
Cancun - 6x weekly B788/789
Puerto Vallarta - 1x weekly B789
Central America
Liberia, Costa Rica - 1x weekly B788
Caribbean
Aruba - 1x weekly B788
Montego Bay, Jamaica - 3x weekly B788
Puerto Plata, Dominican Republic - 1x weekly B788
Punta Cana, Dominican Republic - 3x weekly B788/789
St Lucia - 1x weekly B788
Varadero, Cuba - 1x weekly B788
Indian Ocean
Mauritius - 1x weekly B788
I've underlined the most frequently served destinations from LGW this summer and funnily enough they are the same as the destinations served by the 1x B788 based at BHX this year...... so those destinations are my guess!!..... how did I do conns757?