This is on the CPU-Board, so has a chance of being upgraded in the future.
Temporary update: Pre-orders are currently offered for both 2GB and 4GB units. The 4GB version has been overwhelmingly more popular, leaving some doubt about the mass-production of 2GB units.
Dual Channel PC DDR3L 532MHz:
- 4 Ram-Chips on the CPU-Board at 4GBits density means 2GiB total, confirmed
- 4GB could be possible 
- Chip type: IM4G(08/16)D3FABG Datasheet