The 28 participating teams have been confirmed for the Hong Kong Sevens in March, with Belgium the only newcomers in the main draw.
In accepting an invitation to take part, Belgium become the 57th country to compete in Hong Kong since 1976.
16 teams will compete in the main draw and 12 in the World Series qualifier.
Papua New Guinea and Tonga will represent Oceania in the World Series qualifier, with the winner to earn core team status for 2015-16 season, replacing the lowest ranked side at the conclusion of the current series.
Tonga Rugby's High Performance Manager, Peter Harding, is confident the Kingdom is on course to return to the top level.
"This is the year we are definitely going to get back on the circuit by going well in Hong Kong and in London so we will relaunch this sevens team in Tonga Rugby. You can hang around and play the same level of footy for the rest of your life and you're never going to get any better. It doesn't matter what sport you're in or who you are - the only way you're going to get any better is by playing against better people".
The World Series resumes in Wellington next weekend.