That's a lot of heat to dissipate. Hopefully, they copied Apple's feature of having a heat sensor in the iPad that warns you of high temps (for when you use the machine at the beach in 100 degree sunshine). With the Surface Pro, highly unlikely you will even attempt using it at the beach.
Except that 140 watt is exceedingly false. He was basing that off of a standard i7 processor, not the i5 mobility core which is rated at 17 watts.