Nike shares fell 3% in premarket trading after the struggling athletic apparel giant warned on its earnings call that revenue declines over the next two quarters will be worse than previously expected, underscoring that there is still no immediate turnaround to halt a multi-year bear market that has driven the stock to decade lows."We are not expecting the environment to improve meaningfully over the next six months," Nike's outgoing CFO Matt Friend told investors on Tuesday evening.Customers are "under pressure around the world, and we can particularly see it having a larger impact on sportswear," Friend added.Nike now sees sales…