I think they will.
Ipad/Ipad mini, Ipod/ipod nano, IPhone 6plus/IPhone 6, MacBook/new Macbook, MacBook Air - anyone? Everything they do seems to have a little brother version. While all of those seem to carry the same functions as their sibling product, they serve a slightly different population. It would be easy to remove a few buttons/functions making it cheaper and focus on the sport aspect.
I do however believe that it will be many years in the making. Apple needs to saturate the market with this current do it all device, address the medical community with glucose/insulin type functions first. Once the market slows a bit they may produce a product just for the fitness crowd.
This is pure 100% speculation on my part. If it turns out to be true I am a visionary, if it never happens then I am just a random dude on the internet that cannot be identified