All 12 Principality Premiership sides, along with the top two SWALEC Championship sides Ebbw Vale and Bargoed plus Welsh Students and RGC 1404, will be competing to become the first Foster's National Sevens champions at the all-day event.
John said: "This is the first time our top Sevens players have had a chance to pit their wits against each other in a competitive, pre-season tournament and from the Wales team management's point of view, that is a prospect we are all relishing ahead of the international sevens season.
"There is a real buzz around national and club training looking ahead to Sunday. It will be a real showcase for sevens rugby and a fantastic day out for all the family."
One of the great names of Welsh Sevens rugby, Collin Hillman, will be honoured at the event, with the Foster's Sevens Player of the Tournament award set up in his name.
Paul John, who worked closely with Colin in the build-up to the 2009 Rugby World Cup Sevens, said: "As a management team, we are delighted that the late Colin Hillman will be recognised at the tournament by way of the 'Colin Hillman Player of the Tournament' award. Colin was a great friend and ambassador of sevens rugby in Wales as a former player, coach and team manager.
"He was a Technical Advisor to the squad that lifted the Rugby World Cup Sevens in 2009 and was very much a father figure to many players and coaches who have been involved with Wales Sevens.
"There will also be a charity collection on the day for Amser Justin time, the pancreatic cancer charity for Wales, run by Shan Cothi whose husband Justin also died of the disease."
Although John is Pontypridd's assistant coach, he will not be taking an active role in their bid to lift the Foster's National Sevens trophy on Sunday.
"I'm looking forward to taking a watching brief with a national perspective in mind, with Dale McIntosh and Richard Langmead taking responsibility for the preparation of Pontypridd's sevens side," he added.
"Pontypridd may be top seeds due to our success in the Principality Premiership but sevens is a different game and there will be a huge amount of competition for the silverware on offer.
"All the Premiership sides have got talented youngsters in their squads, Carmarthen Quins have a number of national sevens squad players in their side, Welsh Students are sevens specialists while other clubs will also be strong including Llandovery, Cross Keys, Bridgend and Cardiff as the home side.
"Sevens is a fantastic way to develop players for the 15 a side game, improving skills in both attack and defence and giving players a great insight into international rugby along with being a very intense, competitive and attractive game in its own right.
"We have seen 24 players come through the Wales Sevens system to become full internationals since Wales returned to the IRB circuit in 2005. The most recent examples of this production line are Rhys Patchell, Dafydd Howells and Owen Williams who all represented Wales at Sevens before going on to be capped by the senior Wales side in Japan in June. I'm confident this tournament will help us identify and develop more Wales internationals of the future."
John is also hoping this event, taking place on the new artificial pitch at Cardiff Arms Park, will spark new interest in sevens rugby in Wales.
"We have travelled with Wales Sevens sides to IRB Series tournaments around the world, witnessing some of the biggest crowds and best carnival atmospheres in world rugby," he said.
"The likes of the Dubai, Hong Kong and Wellington Sevens are magnificent global events to be involved with and that is something we would like to strive to achieve in Wales. The Welsh Rugby Union will bid to host Rugby World Cup Sevens in 2018 which is a mark of the importance that is placed on the game and on creating big sevens events for rugby supporters in Wales.
"This is the inaugural Foster's National Sevens tournament, but it is certainly an event we want to grow as we continue to develop sevens rugby at all levels."
Sunday's action begins at 10.20 with top seeds Pontypridd taking on Neath in a mouthwatering opening match, followed by Welsh Students against Carmarthen Quins. The winners of all Round 1 matches will continue into the Cup quarter-finals, while the losers will enter a parallel Plate competition. The finals will take place from 6pm.
There will be a host of live entertainment taking place throughout the day and into the evening, with local band 4th Street Traffic headlining the city centre event.
There will be a kids activity zone with rugby skills workshops, face painting and more, while the RBS 6 Nations Trophy will be on display and available to be photographed. Everyone who purchases a ticket in advance of Thursday 22 August will be entered into a prize draw to win a hot tub for five people to enjoy and the winners of a fancy dress competition on the day will also have the use of an exclusive hot tub.
Tickets are on sale now at just £10 for adults, £5 for Under 16s and £20 for a family ticket (2 adults, 2 children). Go to www.wru.co.uk/nationalsevens to purchase tickets with a free print off at home option. Tickets can also be purchased by calling 0844 8471881 (Ticketmaster) or 02920 230130 (Ticketline). Personal callers can purchase tickets from the WRU shop, 8 Westgate Street or from Ticketline, 47 Westgate Street.
Order of play for Round 1 matches:
Game 1 Pontypridd v Neath 1020 hrs
GAME 2 Welsh Students v Carmarthen 1040 hrs
GAME 3 Bridgend v Cross Keys 1100 hrs
GAME 4 Bedwas v Aberavon 1120 hrs
GAME 5 Llandovery v Bargoed 1140 hrs
GAME 6 Cardiff v Newport 1200 hrs
GAME 7 Swansea v RGC 1404 1220 hrs
GAME 8 Ebbw Vale v Llanelli 1240 hrs