As they carry a 2-0 lead into Sunday's third game of the Stanley Cup final against the Minnesota North Stars, it has become apparent that only one team can defeat the New York Islanders -- the Islanders themselves.

There has been no evidence of that happening this season. The Islanders do not figure to drop four of the next five games after losing only three of their last 32. They want that second straight Stanley Cup, to convince doubters who felt the first one was an accident.

The Islanders are so dominant, so talent-laden, that on paper they figure to rule the National Hockey League for years to come.

Mike Bossy, who has amassed a record 83 goals during the regular season and playoffs, has a devastating shot, with a quick release that leaves opponents hopeless. Bryan Trottier, his center, is a superb playmaker, an excellent defensive player, probably the best all-round forward in hockey.

Denis Potvin is an outstanding offensive defenseman, able to control the flow of the play, and his solid checks leave his signature on victims.

None of these all-stars won the club's trophy for most points collected in postgame three-star voting during the season. That went to Bob Bourne, one of the NHL's fastest skaters and an excellent penalty killer and powerplay specialist.

Mike McEwen and the injured Stefan Person are above-average rushing defensemen. Dave Langevin is a defense standout on the back line. Up front, the likes of Clark Gillies, Bob Nystrom, John Tonelli, Butch Goring and Wayne Merrick never give an opponent an opportunity to relax.

If there is a possible weakness, it is in goal, and when Bill Smith banged his left elbow Thursday there was reason for concern among Islander fans. But Smith, with his remarkable 43-17 Stanley Cup record, is only 30 and there is reason to believe General Manager Bill Torrey will come up with a replacement before the goaltending situation becomes desperate.

Certainly, Torrey has been a magician in the past, in building the awful 12-60-6 team of 1972-73 to its current status. Sixteen Islanders were selected by Torrey in the amateur draft, and not all came, like Potvin in 1973, as the top selection.

Considering the current draft situation, with 21 teams dividing the goods and the 18-year-old crop under surveillance, forcing considerable guesswork by the selectors, it seems unlikely that any other club can match the assemblage of talent on Long Island. Before the cry to "Break up the Islanders" begins, however, it should be noted that the Islanders may begin to break themselves up.

So much success breeds high salaries and a team playing in a 15,000-seat building owned by Nassau County, without the huge television revenues of other sports, cannot afford to keep the troops happy without flirting with bankruptcy. The Islanders are not one of the wealthy teams of sport. Something will have to give, and already the cracks are appearing.

Bourne, more than once in the last two months, has indicated that this will be his last campaign on Long Island. He wants to play in Los Angeles and hopes something will be worked out to accommodate him when he becomes a free agent on June 1. Regardless, he does not expect Torrey, who declines to discuss the situation until the playoffs are over, to meet his demands.

Beyond Bourne, Torrey must consider the players who will be entering the option year of their contracts next season. That group includes Potvin, Bossy, McEwen, Nystrom and Tonelli.

Potvin wants a long-term contract with figures reportedly topping the $600,000 a year earned by the Kings' Marcel Dionne, currently the highest-paid player in hockey.

Bossy, who comes from the Montreal suburb of Laval, has indicated that he would not mind playing for the Canadiens, one of the few teams that could afford to meet his asking price.

The Islanders' dollar demands will be inflated for another reason than ability. Many of them feel that playing on Long Island has cost them endorsements, as well as publicity. They see the Rangers skating in jeans commercials and adorning the covers of magazines and they cannot hide their jealousy.

Any of the Islanders who opted for free agency, under current rules, would be subject to compensation by the team that signed them. The Rogie Vachon-Dale McCourt situation has virtually strangled free-agent movement in the NHL.

A meeting in Las Vegas during the first week of June could alter circumstances dramatically. That is when the owners and players meet to discuss possible changes in the agreement covering compensation. The owners want to retain the present formula; the players desire complete free agency. A possible compromise would be to assign draft choices in relation to player performance.