Constants and variables, that's what it's all about, at least in the world of BioShock. And it seems that one of those infinite doors will soon open and give gamers a new collection of all three BioShock games.

Although game publisher 2K hasn't yet made an official announcement about a BioShock collection, the compilation recently turned up with an Entertainment Software Rating Board (ESRB) rating, suggesting that fans might expect such an announcement soon.

The ESRB listing refers to BioShock: The Collection and offers details about the compilation.

"This is a collection of three first-person shooters in which players assume the role of characters uncovering the mysteries behind the dystopian societies of Rapture and Columbia," the ESRB is reported to have written to describe the collection. "As players explore each city, they use shotguns, machine guns, rivet guns and rocket launchers to kill mutated citizens and enemy soldiers."

The listing also mentions the player's special powers and details some of the violence seen in the game, which results in its "M" for Mature rating. There are also mentions of "sexual material in the dialogue," as well as the use of derogatory language.

The collection will likely include all three BioShock games, and potentially all DLC that followed each game in the franchise. The trilogy of games cover two worlds: the undersea setting of Rapture, as well as the sky-dwelling city of Columbia.

Rumors of a BioShock collection first surfaced last year after a Taiwanese website put up a listing for the game. At the time, 2K refused to comment on the collection's existence and still hasn't made an announcement that such a thing will ever happen. But the ESRB rating is real, and it's likely that this is one rumor that will prove true.

But does this signal a new interest in BioShock as a game franchise? The creator of the series, Irrational Games, shut down back in 2014, leaving the title with 2K, which hasn't announced that it plans on doing anything, at least in the foreseeable future. Releasing a collection, though, could mean that the company plans on seeing if continuing with the franchise is worth it, depending on sales, allowing fans to request more BioShock with their wallets.