The best way to prevent LogoFAIL attacks is to install the UEFI security updates that are being released as part of Wednesday’s coordinated disclosure process. Those patches will be distributed by the manufacturer of the device or the motherboard running inside the device.

Supposedly today? Depends on the manufacturer

No. Every vendor is going to need to patch their shit, so most likely the OS’s are going to kludge something on top to try to prevent uploading logos.