A longer battery life, perhaps. But it certainly won't be 'Lite'.
The 3DS as it is is as small as it can possibly be. They had a lot of trouble just fitting everything into the shell whilst making sure it was still durable and the cooling was still sufficient.
And also, to have a longer battery life, the 3DS would need a physically larger battery, and therefore if they do release any upgrades (which they probably will eventually, but not for quite some time), then it'll probably be along the lines of an XL version, with a larger body and larger screens.
Why do you believe this, exactly?
No-one is forcing you to buy the new iteration. The old one is just as effective.
What's more, you appear to think that Nintendo are somehow purposefully holding back when they release a new console, just so they can release a second version. I can tell you that when they released the original DS, with the technology and production means they had available to them, they could not make it any smaller. It was only with more than a years worth of extra work that they managed to shave it down.
And you say they 'always' do this? The Wii has not had any new version, neither did the GameCube (i'm not counting colours here, only actual hardware redesigns. If you're stupid enough to buy a console you already have again just because a new colour has been releases, then you deserve everything that's coming to you).