They have hired people with phds on much more ambitious non invasive sensors: blood sugar, blood oxygen etc.Im thinking the sensors may be along the lines of Altimeter, Barometer, and Compass. Cellular may be a while off due to size and battery. I read an article stating they may even keep the same design and just do a speed bump and better battery. None of us will really know until an Apple Executive steps up on stage and announces it.
No leaks on cellular radios yet. Hopefully just too early.I think the current size is great expect for thickness. I think a cellular chip will be part of the watch next version. Long term if apple wants to see crazy growth they need something like glucose levels and blood pressure as sensors. There are already products that can determine blood glucose levels without blood so if anyone can get it into a form factor like a watch-it's apple.