Apple acquiring Fitbit would hurt Fitbit's sales for sure. Many users use android based devices with their Fitbit device and by Apple acquiring them, they would lose those customers as it would become a 'Apple proprietary' device.
I personally like Fitbit more and I think many of the people will be going for the same, mostly because of the price issues. Recently heard about the company a lot for it's booming turnover and it's Upcoming IPO