From what we can tell, this new S-Class will be more of a refresh than a complete redesign. The nose looks mostly the same, but the headlights have changed. Instead of a single string of LED lights, a trio of slender light bars are used for accent lighting. We can also just make out the top of the front bumper, which seems to have a different shape than the current model.
There's further reason to believe this new S-Class is just a refresh. Last summer, a product release plan leaked out, and it shows an "S-Class facelift" for early- to mid-2017. According to the official Mercedes announcement, this facelifted car will have notable upgrades. It says the S-Class will have new interior amenities and assistance systems. We would guess those assistance systems are related to semi-autonomous driving. The company says new engines will be shown, too, but doesn't say whether those engines will be used globally. The S63 and S65 AMG models will also be on display in Shanghai alongside the standard S-Class.
Less information was given about the Concept A Sedan. However, considering the name, it's not surprising that Mercedes says it will be a preview of future compacts. Expect it to be an early look at the next-generation CLA sedan.