With only nine months left until the showpiece begins, Laporte is looking to finalise the group and he will be hoping the forthcoming RBS 6 Nations Championship provides him with some clues.
The 40-man Les Bleus squad for the Six Nations was revealed on Thursday, with four uncapped players making it into the party.
Those not selected - except for Frederic Michalak, the mercurial fly-half who is currently out injured - will struggle to make France's 30-man World Cup party.
And Laporte acknowledged there was not much time left to impress him and his backroom staff.
"If you take the squad of 40 that has been announced, and add some names we have mentioned in private, we are not far from the France team, at this moment in time," he said.
"It is a base we are working from.
"The door is not closed to anybody. But with the 20 players who are certainties - save for unexpected hiccups - to figure on the list of 30 (for the World Cup), there aren't many opportunities left."
He added: "The squad is always evolving, it can alter as a result of injuries or changes in form.
"The true squad of 40 will be the one we communicate on June 14, at the end of the (Top 14) championship.
"But in revealing these 40 names (for the Six Nations), it signifies that we are in the home straight."
The quartet called up for the first time were front-row forwards Benoit August and Laurent Emmanuelli, centre Romain Cabannes and full-back Anthony Floch.
Clement Poitrenaud, Nicolas Mas, Jean-Baptiste Poux, Sebastien Chabal and Sebastien Bruno were also included after spells in the international wilderness.
Chabal, the totemic Sale Sharks number eight, has been particularly impressive in recent months, and Laporte hopes the hirsute former Bourgoin player can reproduce his club form on the international stage.
"We are hoping to see Sebastien in the France team, at the level he is performing at Sale. It is our biggest hope," said Laporte.