The next generation of smart phones, with there larger sizes, should spell the end of the small tablets. I personally think the SP3 is pretty damn close to being the ideal tablet. If the rumors or correct that the new Intel chip set they might use is less powerful than what we can get in the SP3, than I can't see myself upgrading.
Why bother with a chipset that is less powerful and only a 30% savings in power. The CPU is only portion of what runs down the battery. I can't see Microsoft being stupid enough not to make a major upgrade in power with the SP4. I would like to see it add a little lighter, a 2nd USB3 port, a new revision of the HDMI standard video output, more memory capability, & a little sturdier keyboard.