The much anticipated PrestaShop 1.5 release will have a number of new features including multi-store management. With multi-store management you will be able to manage multiple stores from a single Back Office. PrestaShop 1.5 beta has just been released on 12th of June. My guess PrestaShop 1.5 final it will be ready for production in 3-6 months time. Hopefully much earlier.
Here is the official link to PrestaShop 1.5 roadmap: PrestaShop 1.5 Milstones