Twitter account posts image from original BioShock, asks fans what it could mean.
Has been profitable for the publisher thus far.
The Bureau and BioShock 2 developer has confirmed staff reductions, but full closure is expected.
BioShock Ultimate Rapture Edition, a bundle featuring the first two BioShock games and all DLC, has been listed by the BBFC.
"It's always about the stars aligning. We're still focussing on it, but it hasn't consumed us so much," says the Irrational boss.
Ken Levine has cast doubt over plans to turn BioShock into a film, stating that Irrational has "no need" to see the project come to fruition.
Money men not interested in backing his R-rated vision.
Irrational discussed making sequel, but felt it would be repeating itself.