Gethin Jenkins, Luke Charteris, Huw Bennett and Aled Brew follow in the footsteps of Mike Phillips, James Hook and Lee Byrne in going to France, while Scarlets' Ben Morgan will turn out for Gloucester next season.
Coupled with the fact that Cardiff Blues, Newport Gwent Dragons, Scarlets and Ospreys all agreed to a salary cap of £3.5million starting next season, and things don't look rosy for the regions.
But while admitting it will be hard to keep everyone in Wales, Lewis is adamant they can prevent another mass exodus to a French system that he describes as 'unsustainable'.
"We need to do everything we can to keep our players here and the way we're going to do it is by working together with our four regions," said Lewis.
"You will not keep all of your players in one country. That simply doesn't happen. People want to experience other things.
"But we must keep as many players as possible here in Wales.
"The way we are going to do that is by creating an environment here in Wales which is so attractive that players simply will not want to leave.
"And underpinning that has to be the finances that we can compete with as many of the clubs, provinces and countries in the world game.
"We won't be able to compete with everyone simply because it's a matter of numbers.
"The salaries that are on offer, particularly in France, are simply unsustainable and also unrealistic.
"I simply think it cannot continue at this pace. We've seen that already in France - Stade Francais was one of the biggest clubs in France with one of the biggest wage bills.
"That has now gone and those players have left. We've seen it time and again [with] numerous other examples.
"It's not sustainable but in the short term it can be extremely attractive for certain players and that's what we need to address."
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