Some critics may wish he would retire, but others believe the media mogul is at his most powerful

Rupert Murdoch turns 80 on Friday, which has prompted this MediaGuardian special looking back at the mogul's career and, in the case of this piece, looking forward into the future for News Corporation, the behemoth he built along the way. Yet while critics may wish the Australian-turned–American would simply retire, in truth the business he runs has never been more powerful than it is now, as he stands on the threshold of completing his biggest ever transaction, the £8bn or so buyout of BSkyB's other shareholders.

Those who work for Murdoch talk about a man reluctant to discuss his age – although one long-serving London-based executive was advised to mention diets as a way of making conversation with a man careful to maintain his health despite a punishing travel schedule.

Even the suggestion he might be slowing up is dismissed internally. When this writer, while working at the Times, was advised by sources at HQ that Murdoch would "travel less" after it was announced that his son James would join the business to run News Corp Europe and Asia in 2007, the phrase was struck out by those more senior.

On the face of it, his recent moves could be argued as forming part of a tidying-up which prepares the company for whenever Murdoch does choose to retire. Not only is BSkyB – the business previously run by his heir apparent and youngest son James Murdoch – being brought into the fold, but there is now a company role for daughter Elisabeth following the agreed £415m purchase of her production company Shine. Both sit on the board – as does brother Lachlan, the middle child from Rupert's second marriage, but he remains for the moment outside the business, building up media investments in Australia.

However, as News Corp's infernally complex capital structure – and family interests – have gradually been simplified there is little sign of Rupert losing his way. "I had lunch with him recently," says Kelvin MacKenzie, who edited the Sun through most of the 1980s. "He was going on about the iPad this and internet that. I think he's 80 going on 18." And while that may be something of an exaggeration , there is no obvious sign of the man's power diminishing.

Murdoch's great skill has – again, and again – been in deploying profits from one business to invest in growth elsewhere, creating the Sun, the Fox television network, and Sky. While other newspaper owners have been mesmerised by that business, Murdoch has simply scooped up papers and moved on. Back in 1987, after the Wapping restructuring, News International in the UK earned £150m – which compares with £107.3m in 2008 and £27.3m in 2009 as the recession hit. So while the newspaper business has barely grown, and remains a drag on Wall Street's perception of the business, News Corp has diversified into TV so successfully that once the company completes the buyout of BSkyB it will generate at least $4bn of cash after tax a year.

"The question will rapidly become," says Rich Greenfield, a New York analyst with BTIG Research, "what will Rupert do with the cash?" News Corp has tended to trade at a discount to other integrated media groups, the likes of Disney and Time Warner, because of a "Murdoch discount" in which investors fear that the company's leader only reluctantly offers share buybacks or high dividends in preference to acquisitions. "He scares investors because he disregards near-term considerations."

There may remain no shortage of near-term controversies. The News of the World phone-hacking stink threatens to worsen in coming weeks, as more lawsuits emerge, and even Roger Ailes, the Fox News boss, has been hit by allegations that he encouraged a former colleague to lie to federal investigators. But News Corp's newspapers are rounding errors in a company on track to generate 75% of its $7.2bn operating profits from US cable channels and satellite broadcasters around the world next year.

On this prospectus it does not matter that Murdoch has consistently failed to get to grips with the internet, with the failure of MySpace the most obvious recent example. While businesses like the company's Fox film studio – the Avatar blockbuster apart – may be operating in a mature market, there is plenty of growth coming from subscription television, not just in the US, or with Sky in the UK, but with the earlier stage Sky operations in Italy or Germany. And it is James Murdoch's job to cast around for more countries to populate with more Skys to come.

Even the US Fox television network – supposedly a mature business also – is now targeting $1bn of profit (twice this year's anticipated level), partly because News Corp is hoping that it can run two $800m reality television hits in a year: American Idol where Simon Cowell used to judge, which has held up better than expected in the first year after his absence, and the new US X Factor, which comes to screens this autumn, and whose importance to Cowell and Fox is so great that it may see the impresario disappear from ITV.

Fast forward to 2015, and News Corp is predicted by BTIG Research to have worldwide revenues of about $44bn, with BSkyB included, and pre-tax profits of $8.7bn. When MacKenzie says that News Corporation is "in the best shape I can remember" his words are not those of a Murdoch-booster, but an accurate assessment of a remarkable 20-year recovery for a company that was once a phone call away from going under as the losses from the infant Sky soared.

It is, in short, an astonishingly bountiful inheritance, for a business that Murdoch has always intended to be run by his children, as his former deputy Peter Chernin told Steve Hewlett for a BBC radio documentary. Those who believe – or hope – that there is a strong sibling rivalry among the next generation are sorely mistaken, but the hard part will be keeping together the Murdoch Family Trust that owns nearly 40% of the voting shares when each of his six children by three marriages share an economic interest.

Yet, even that is some way in the future. Rupert Murdoch's battle to get the BSkyB deal through is unlikely to be his last significant act.