A new report from industry analyst NPD has predicted that Mac sales will see a small year-over-year decline in sales again, mostly (and somewhat ironically) due to the industry-wise cannibalization of traditional PCs by the iPad. While still likely to beat the industry average rate of decline, Apple had until last quarter been able to continue growing Mac demand thanks to a greater emphasis on notebook sales. Apple missed expectations for Mac sales last quarter, but may have a chance to reverse its fortunes in its fiscal first quarter this winter….