As readers of our fashion pages already know, men's suit styles move in cyclical patterns; a year or two of frenetic changes is usually followed by a period of relative calm, once a fresh norm has been established. It's playboy's prediction that suits today have reached such a plateau and will most likely continue on an even keel for at least several seasons--and possibly longer. We foresee that the predominant style for this fall and winter will be a continuation of the already popular wide-lapelled and slightly flared-leg two-button model, interpreted in new colors and fabrics--including single and double knits, wools, worsteds, synthetics, corduroys and velvets. Expect overcoats to be somewhat less flamboyant than they've been in seasons past, the costume look having been transformed into a tasteful assortment of single- and double-breasted coats (many of them belted) that extend to mid-calf. But if you're concerned that well-dressed males this fall will look as though they've all been pressed from the same cookie cutter--not to worry; you'll find plenty of ways to express your individuality in the shirt section of most men's boutiques and haberdasheries. There you can choose from geometrics, floral and motif prints (such as an allover bird pattern), earth-tone plaids and printed knits, most with long-pointed collars. And in case you haven't heard, the white dress shirt has been elegantly resurrected, notably in white-on-white stripes. Ties, incidentally, are holding steady at four and a half to five inches in width. In casualwear, look for jean suits, shirt suits, coat suits (warm coats with matching trousers) and plenty of leisure leathers--suedes, buffed pigskins, cabrettas and even buckskins that resemble blue denim cut into a variety of tops (many with coordinating slacks). Whatever you choose, be assured that there are more than enough fashion ways to express what you think through what you wear.