As much as Sky knows its future is inextricably linked to the outcome of the next All Blacks broadcast rights negotiation, New Zealand Rugby also understands the next deal has the power to make or break the game in this country.

TV income accounted for 40 per cent of NZR's $257 million revenue last year, and this year, when there won't be a $40m injection from hosting the British and Irish Lions, broadcast rights are likely to constitute more than half its total income.

For more than 20 years, Sky has been the sole TV rights holder of All Blacks tests and have probably, in that period, spent somewhere in the vicinity of $1.5 billion to secure their exclusivity. It has worked for it, though, as its ownership of rugby has been critical securing in excess of 700,000 subscribers.

Rugby is also primarily the reason Sky has been New Zealand's most profitable media company for the past 20 years. But this mutually beneficial relationship is no certainty to survive beyond 2020.

Sky didn't face any real competition to secure the current rights when they were agreed in 2014. It had the right to make the first bid — uncontested and undisclosed — and if it was high enough, NZR wouldn't open the floor to any other company.

Sky doubled the value of the previous deal that ran between 2011 and 2015 and NZR accepted, knowing it would be banking between $80m and $100m in annual broadcast income from 2016 to 2020.

Technology, consumption habits and the media landscape have all changed dramatically since the last deal was struck and there is massive uncertainty about how the next negotiation will play out later this year.

No one knows yet whether new bidders such as Amazon, Netflix, Lightbox and Vodafone — and maybe others — will enter the fray. Nor does anyone have a good feel for what digital rights — the ability to stream tests — could be worth and how they will be sold in conjunction with traditional terrestrial TV rights.

All that NZR can be sure of is that its expenditure forecasts are rising and that if it wants to keep the best players in New Zealand, there is no effective mechanism to slow the outpouring of cash.

The national body can predict its income — because 80 per cent of it is secured through long-term broadcast, sponsorship and licensing agreements — with certainty through to the end of 2020 and also its costs.

The accounts balance through to 2020 but to sustain that, the next broadcast deal has to be bigger than the existing one.