Reading various permutations of the information - on the BBC site - the suggestion is that the project will indeed be ongoing each year, though the actual hardware may be upgraded from time to time - as with the B+ but perhaps more readily, being a lower cost device. (The price of the Pi is disappointingly sustained - need I mention?)
Clearly a LiPoly battery is part of the plan for stand-alone use (which will define the standard operating voltage), a sleep mode and so on. High efficiency SMD LEDs can be multiplexed for just a few mA total.
Now as to the wider distribution - as most of us will of course
want one just to play with (missed out on the OLPC) - if we look at the Arduino model, that should be adequately catered for by our friends in the Orient.
Thinking on this for a moment (my wife immediately twigged to the prospect of wholesale "shrinkage"/ school black market and such), I have a notion it will go reasonably well. Outside of the initial novelty of wearing a scrolling "F*** You!", it should actually lead to firstly, an "app" trade for novel, well, applications and a healthy level of competitive creativity to exhibit and/ or provide such "apps" for trade. It should
lead to some actual social value attached to coding skill.