The Scarlets are set to do battle with the Newport Gwent-Dragons followed by Cardiff Blues against Ospreys at the Millennium Stadium on March 30.
The fixture is set to be an annual occurrence for at least the next four years and Lewis has highlighted the major benefit to fans being the opportunity to watch two Welsh derbies for £25 for adults and £10 for those under 18s.
The double-header format has been a popular curtain raiser to the English Premiership since 2004 where London's four largest clubs are on display in front of a regular crowd of more than 50,000 at Twickenham.
The timing of the Welsh double header falls just after the end of the Six Nations and just before the RaboDirect PRO12 moves into the business end of the season, enticing clubs to throw all their stars into the fray in the quest for much needed points to ensure a place in the play-offs.
And Lewis is adamant that the Welsh rugby public will immediately take to it, and keep returning for years to come.
"This unique double-header will be a historic moment for Welsh rugby," said Lewis.
"It has taken us five years to put this fixture together, but I am confident it will have been worth the wait.
"The WRU will promote and underwrite this fixture for the next four years, that's how much we believe in it.
"Fans will see the stars of Welsh rugby and get two derby matches for the price of one very reasonably priced ticket.
"I predict this double-header will become a highlight in the Welsh rugby calendar for a long, long time to come."
Ospreys' chief operations officer Andrew Hore echoed Lewis' belief the public will turn out in numbers to the event next spring, particularly if the Welsh regions are contesting for the RaboDirect PRO12 title.
"From a rugby perspective that end of Easter period used to always be extremely popular and I know it's something that Roger Blyth (Ospreys managing director) emphasised as well was getting back to that time of year being important for both rugby and the crowds," said Hore.
"This hopefully will give it that impetus and as we showed last year you can still have a hell of a run and as the stats show when the Dragons came down to our place last season you still had near on 14 and a half thousand people so there is desire, even at that time of the year, if here's enough riding on it for people to turn up."
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