If you previously purchased Mark of the Ninja (classic) on your Steam or Xbox Live account, you will be able to purchase Mark of the Ninja: Remastered at a discounted price of $4.99 USD.
If you previously purchased Mark of the Ninja: Special Edition on your Steam or Xbox Live account, you will automatically get Mark of the Ninja: Remastered for free.
Please note that the upgrade paths are restricted within a particular platform ecosystem. Existing Steam players may upgrade on Steam, and existing Xbox 360 players may upgrade to the new Xbox One versions.