Louise Evans from business advisors Grant Thornton says promotion could be worth up to £150m for the club and will have knock-on benefits for the city and Wales.
More top news
Sheffield Wednesday secured their place in this season's Championship play-offs with a 3-0 victory over their nearest challengers, Cardiff.
Two tries in the last six minutes from Ospreys skipper Rhys Webb won a thrilling Welsh derby at the Principality Stadium.
The oldest ever rugby jersey to ever go on public sale could fetch as much as £20,000 at an auction next month.