In the past decade or so, there has been phenomenal growth in the number of people arming themselves with tennis rackets and setting out to do battle on the courts of America. Amid this tremendous infusion of interest in the game, the question arises, what is next for amateur tennis?

Precisely what shape the game will take in the 1980s and '90s is hard to tell. But some definite and potential trends are clear: The amateur game will change dramatically if and when tennis becomes an Olympic sport. And the sport will be further remolded by the increasing presence on courts of the relatively young, the relatively old, the black and the Hispanic.

The most dramatic change would be brought on by the probable reinstitution of tennis as an Olympic sport at the '84 Games in Los Angeles. If this happens, the areas of the game most benefited would be those most in need -- college tennis and women's tennis.

College tennis, especially among NCAA Division I schools, has witnessed mass defections of major stars to the pro ranks the last few years.

A recent example is John McEnroe, who left Stanford after his freshman year.The list is long: Jimmy Connors, Eliot Teltscher, Peter Fleming, Brian Teacher and Billy Martin all left UCLA before their eligibility expired. Tracy Austin and Pam Shriver never will even go to college.

But tennis as an Olympic sport would slow this exodus because it is a safe bet that our best amateurs would be college players.

Title 9 of the Education Amendments Act of 1976 also would receive a boost if the International Olympic Committee gives tennis the nod for the '84 Games.

Title 9 simply states that if a college or university receives federal funds, then that institution's athletic program must equally benefit women as well as men. Along with swimming and basketball, tennis is a very popular varsity sport for women. The prospect of a gold medal is sure to give women's tennis at the college level added emphasis.

Another trend at the amateur level will find junior development programs making further inroads into the public school systems. The perennial problems here have been lack of both facilities and qualified coaches. Many urban high schools do not have the space for three to five courts, and far too few high school coaches played college tennis.

Today's innercity high school tennis coach is likely to be an academician rather than a member of the school's athletic department. The reason: Tennis usually runs a distant third to baseball and track as a spring sport, so it suffers from lack of attention.

All of this is changing. There is renewed emphasis on orienting new junior programs toward the public schools rather than the public parks. While the suburban schools generally have more money, coaching, and facilities, the best athletes are found in the central city schools. Recruiting by the suburban high schools for their tennis teams also has tended to reenforce their supremacy.

Two additional amateur trends deserve a mention. Look for more minorities and more middle-aged tennis players in the '80s. Lured by the money in the pro ranks the increasing availability of public junior programs, and tennis on television, the nation's minorities will make major contributions to amateur tennis programs at all levels.

But no trend excites me as much as the interest our middle-aged citizens are showing in instructional programs. By 1985, one-half of our population will be over 50. A good number will want to play tennis. It will help keep them out of the doctor's office and go a long way toward assuring them a good night's sleep. Tennis camps already are experiencing an increase in their participation.

While the increased interest shown by blacks, Hispanics, and the over-45s is sure to give tennis a boost, their presence might make different demands upon the tennis market. Black and Hispanic interests will add to the demand for more public courts, which already is a problem in many of our urban areas.

But added players in the 45-and-up category could bring about a demand for a smaller court. Many of our older players complain about the inability to enjoy a singles game on a conventional 78-by-36 court. It just is too big and therefore they are forced to play doubles, not because of the cost, but because 50-year-old legs find great difficulty in covering the courts.

Given the reluctance to fiddle around with such standard parts of the game as court dimensions, it does not surprise me that no one has come up with a handicapping system. The problem is to produce some universally acknowledged common denominator against which one can measure individual performance. A handicapping system would do much to stimulate interest -- and arguments.