Six Nations chiefs admit the competition could go behind a paywall from 2022 but insist the tendering process is still at an early stage.
A report states that Sky Sports are favourites to secure the next broadcasting rights package in the UK in a deal worth in the region of £300million (€344 million).
BBC and ITV are contracted to share all games until the end of the 2021 Six Nations but rules prevent them from making another joint bid.
It raises the prospect of the hugely-popular tournament no longer being free-to-air, but event organisers insists no decision has been made.
"Six Nations are in the process of seeking bids for various sets of media rights but these are not due for some time," a statement read.
"All of this is highly premature and speculative as no proposals have yet been received by any interested party.
"We would not rule anything out at this stage and the unions will collectively review and make a decision based on the nature of the offers received."
Virgin Media currently hold the rights to the tournament in Ireland, up to and including the 2021 edition.
The process for the next Irish rights agreement has also not reached bidding stage.
Irish law currently mandates only that deferred coverage/highlights of the Six Nations matches be available free to air. Events that are protected for live coverage include the All-Ireland hurling and football finals, the Republic of Ireland's Euro and World Cup qualifiers and tournament games, and the Aga Khan Trophy.
Six Nations chiefs' refusal to rule out the possibility of pay per view has resulted in a motion being tabled to the UK Parliament demanding that it remain free to air.
Kevin Brennan, MP for Cardiff West, has submitted the proposal that has also been signed by a further 11 Welsh MPs.
Brennan is proposing that the competition be "put in the government's 'Category A' of sporting events", thereby ensuring it will be shown live on free-to-air platforms. It is currently 'Category B'.
The motion also recognises the terrestrial viewing figures generated by "one of the oldest and most historic sports tournaments in the world" and the role it plays in inspiring children to play the game.