According to Synthtopia, the kit will come with enough pieces for a decent Monosynth, packing parts like an envelope generator, oscillator, mini keyboard and MS-20 filter to build with. I'm sure the intention is to build using more than one kit and make a phat little synth monster!
I've come across modular electronics toys before, so the idea is not necessarily anything new, but the Little Bits gear is well made and built for fun, despite being fairly expensive. So far, the videos of the first demonstration are very promising, with sequenced blips and blops, delay effects and so on that make for useable sounds and fun musical experimentation.
The idea is that you can build prototypes fairly quickly and easily but as with all building toys it steadily gets more complicated the more you buy and with the open source nature of the Little Bits, more complicated modules will be available owing to demand and creativity of the end users. There's even a lovely page called Dreambits on their web page for suggestions and based on recent feedback, modules for Eurorack, MIDI and CV outputs to work with existing setups are high on the wish list.
So add some "serious" synthesiser kit with signature elements like the MS-20 filter from Korg that can interface with itself and you can build some complicated modular gear with some weird and fun input/control sources. I'm thinking light sensitive stuff for filter or pitch control, perhaps.
One user on Muffwiggler sums it all up succinctly, given how Korg are really stoking the amateur music scene at the moment.
It remains to be seen exactly what you get in the kit, as Korg already have me invested in the Korg Volcas. However, at a price point of 16,000 Yen (just over £100 according to XE.com) it will sell like hot cakes and certainly be a gateway drug for Little Bits users and hopefully drive development of bigger and better modules. All exciting stuff!
http://jp.littlebits.com/synth/ (down at time of writing, probably offline due to stress!)