We'll have to wait and see what the battery life of the Surface 3 is really like. If it's in the 9-10hr range, then I'm not sure what an additional 30% power improvement is really worth. Once the battery can get you through the entire day then it's going on the charger that night anyway, the extra battery life would only get you through your first meeting. I would expect most manufacturers to reduce the battery size to save weight while keeping that same 9-10hr battery life. This will shave valuable weight off the device but it's not going to save 30% of the machine's weight, maybe 10-15% instead.
Also I'm really skeptical about that 30% claim. Haswell was similarly hyped but resulted in more like 10-15% improvement IIRC (trying to find the anandtech review) - most of the rest of the improvements in battery life came by underclocking it (ex. Macbook Air) and motherboard improvements.