MakerDAO’s new innovation, Multi-Collateral DAI (MCD) is planned for release this month pending a vote. Since everyone should be moving to MCD, Maker wants people to call the old DAI, SAI.
The reasoning behind this is to start spreading awareness to the differences of DAI and MCD. DAI is created by sticking Ethereum in a contract. In order to get the Ethereum out, you need to put as much DAI back in as you got out of it, plus interest.
Once MCD releases, people will be able to create DAI with more than just Ethereum, hence “multi-collateralized.” Maker chose to replace DAI’s name with SAI to emphasize that it is the singularly-collateralized version of the product.
“to help users and others distinguish between Dai generated via SCD and Dai generated via MCD, we will begin referring to SCD-generated Dai as Sai, and MCD-generated Dai as Dai. We urge all in the Maker community and in the media to do the same.” - MakerDAO
Another reason they might want users to get SAI into their thick skulls is because they will be responsible for converting DAI to MCD. If it is not converted, they risk losing money to volatility as the asset will start to reflect the value of Ethereum, according to Compound.