Had a live chat with Samsung today, here is the conversation. Looks like they are pushing it off to Microsoft.
Stacie: Hi, thank you for contacting Samsung Technical Support. How may I help you today?
Visitor: When is WP 8.1 going to be available for this device?
Stacie: I understand that you are looking for the availability of a service for your device.
Stacie: I will do my best to assist you in this regard.
Stacie: In order to assist you better and to gather information,Please provide me with the model number of your device. It should be found in (Menu>> Settings>> About Device) or you can find it beneath the battery. It generally starts with SPH,SCH,SGH,SM.
Visitor: SM-W750V
Stacie: Thank you for providing the model number.
Stacie: Please be specific with the WP 8.1 you are referring to?
Stacie: I will do my best to assist you with the required information.
Visitor: Windows Phone version 8.1 operating system.
Stacie: Thank you for confirming.
Stacie: I appreciate your intention and curiosity. We at Samsung live chat support do not have the information about the future updates and releases.
Visitor: Who would?
Stacie: Please understand that Microsoft releases new versions for the devices.
Stacie: Also Please understand that we are not aware of the future releases even with the android at technical support.
Visitor: So, how about the firmware for this device to support Windows Phone version 8.1? Microsoft doesn't also release firmware for Samsung devices, do they?
Stacie: Please understand that Microsoft releases the firm ware too.
Visitor: Okay, thanks. I will check with Microsoft.
Stacie: You are welcome.
Stacie: It was pleasure assisting you.
Stacie: Is there anything else I can assist you with?