While memory doesn't sleep, DDR4 supports Deep Power Down and Low Power Auto Refresh even in the non-LP form factor (this is 50-80% power reduction, there are also variable timing modes which can be used to reduce power consumption during normal machine power states).
I am ok with the LPDDR3 being used for the 13" one, but on the 15" they should've went with DDR4 tbh.
As for the chips yes no quad cores for KB yet, but then again I don't understand why they didn't just staggered the release like usual, MBP13 can come out with Kabby Lake Dual Cores and the 15 can come out later when the QC's are out which is December this year.
As for the 7th gen CPU--there are no available quad cores. I don't think Apple wanted to release redesigned MBPs with the 15" flagship model having a CPU one-generation behind the 13" model.