I think both will launch this year, and both will be fairly expensive to start. Both Sony and Microsoft will milk PS360 for at least one year and present their new systems as elite options. I think minimum $400, though $450 or more is very possible for straight up cash purchase. MS will likely try to hide the high price with a subscription. Both companies will sell at a loss. If sony incluses a WiiU-like tablet pad, costs will go up. I think both companies will be OK with starting sales slow, then increasing over time as PS360 die.
As far as "power" goes, it's hard to put a number on such things. The CPU's will be increased, but the tangible benifit is marginal to games. The GPU's will be much better, but the old GPU's were already pretty good. There is a pretty solid rumor out there from former AMD employees who are being sued because they leaked info about PS720. Since they are being sued, I expect they were telling the truth. The rumor pegged the graphics cards as being somewhat modest by current PC standards, which is to be expected. They would fit somewhere above WiiU and below top PC's. The RAM is a big question for me as it can have a big benefit to games and open up some new possibilities. I would expect at least 4 gig, at most 8. Either way you are talking a minimum of 8X the room to work as what you are seeing on PS360 which is pretty dramatic.
So my wortless prediction is $499 systems, with MS offering a $299 price with costly subscription. XBox - 8gig RAM. PS4 - 4gig, but a slightly more powerful graphics chip. They will be similar in power and cost, upwards of 8X as powerful as PS360 and 2-4X the juice of WiiU.