Wales went within a whisker of reaching the World Cup final against New Zealand next Sunday, losing 9-8 to France despite having skipper Sam Warburton sent off and seeing prop Adam Jones depart injured inside the opening 20 minutes.
They will now face Australia in Friday's bronze medal match, having spread a huge feelgood factor about the way they play the game and how it is underpinned by an exciting young generation of players like Warburton, George North, Toby Faletau and Dan Lydiate.
Coach Warren Gatland is under contract until 2015, while a deal was struck earlier this year with the players to 2016.
"It truly is an exciting period," Welsh Rugby Union group chief executive Lewis said.
"This is most probably the first golden era of Welsh rugby in the professional era.
"This tournament has been an absolutely resounding success for Welsh rugby.
"It has given us all a great deal of confidence, it has given us all a greater pride, it has given us a sense that we have such an exciting future ahead of us."
While Gatland's future with Wales appears long-term, though, defence coach Shaun Edwards' contract expires after the tournament and backs specialist Rob Howley has been strongly linked with a move to Aviva Premiership club Bath.
Edwards is currently head coach at Wasps, and Lewis said: "Any discussion about Shaun's future has to take place first with Wasps.
"There is no doubt he has been absolutely outstanding for Welsh rugby, and I am on record for saying that, but there is not a lot we can say until we have had that conversation with Wasps, out of respect for his position with them.
"They have always been his principal employer. Let's wait until this World Cup is over, and in the cold light of day we can consider the future.
"I can remember four years ago we had very long and protracted discussions with Wasps about the release of Shaun. You have to respect that employment position.
"It has to be one step at a time because of the respect I have to show when he is under contract to someone else. You cannot induce someone to break a contract - that is a serious legal point.
"We have to talk to the right people at the right time.
"I was able to negotiate with Warren last year to secure his services for the next four years because we were his principal employers.
"From the Welsh Rugby Union's perspective we are absolutely delighted with the coaching staff. It is a great team effort and they complement each other perfectly. It is an outstanding team."
More than 60,000 people watched Wales face France on giant screens at the Millennium Stadium, and Lewis confirmed the exercise would be repeated for Friday's third-place clash.
"The energy that has been created by this group of players, it's so powerful that we have now got to harness it and drive the game forward in Wales," he added.
"The next four years is going to be so exciting for this coaching team and this group of players.
"After what they have achieved here and all the hard work they have put in over the last few years, they have now got it all ahead of them.
"If you think about it, Grand Slam in 2005, Grand Slam in 2008 and here we are, semi-finalists in the Rugby World Cup.
"But look at the age of these players, look at what they have achieved thus far. Everybody wants to keep this together."
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