IMPORTANT: This is standard procedure, not some jerry-rigged, conspiratorial, process invented to delay the report. Also note: This isn't a matter of, Hey, c'mon in sometime when you get a chance. As you'll see, below, OIG is scheduling this review: Each principal gets a time when they can come in and review the portions that OIG determines are relevant to them:
AP - The Justice Department’s watchdog is nearing the release of its report on the early stages of the FBI’s Russia investigation, a document likely to revive debate about a politically charged probe that shadowed President Donald Trump’s administration from the outset.
The inspector general in recent days has invited witnesses and their lawyers who were interviewed for the report to review portions of a draft this week and next, a critical final step toward making the document public, according to multiple people familiar with the process who insisted on anonymity to discuss it.
As part of that process, the people will have opportunities to raise concerns or suggest potential edits, making it unclear precisely when in the coming weeks a final version could be ready for release. Inspector General Michael Horowitz told Congress in a letter last month that he did not expect a lengthy review period and that he intended to make as much of the report public as possible, with minimal redactions.
And the WaPo gives their version, which is very similar and posits the same timeline:
WaPo – The Justice Department inspector general has begun scheduling witnesses to review draft sections of his report on the FBI’s investigation of President Trump’s 2016 campaign — the clearest indication yet that the long-awaited document will soon be released publicly, people familiar with the matter said.
Several witnesses have been scheduled or are in talks to review sections of the report dealing with their testimony in the next two weeks, the people said on the condition of anonymity to discuss a sensitive matter. That could mean public release is imminent, though the witnesses will be allowed to submit feedback — which could spark more investigative work and slow down the process.
The particulars for each witness’s review were not immediately clear and in some cases were still being negotiated. The inspector general’s office will probably offer relatively short windows for witnesses to submit feedback and take other steps to prevent leaks, as it often does in sensitive and high-profile cases.
So it won't be much longer.