At first glance this looks like a shrewd move by Obama to box in both Trump and Russia but lets think about it for a second.
Trump and Putin want peace with each other. If their administrations are successful, there's some mutual benefit. If Trump could strike a major bilateral accord with Putin, it would probably be seen as one of the great peace deals sense the end of the Cold War. Trump could hang his hat on a major foreign policy accomplishment.
Obviously accords like that involve give and take. Trump can be like

those sanctions were already in place. I'll take them off but only if you give us X when we're signing our big treaty that is going to make us all look great and hopefully ensure world peace. If he can pull it off, it could be yuuuge, bigly.
Remember, Russia isn't inherently evil. They're only "evil" because they don't bow to our every wish.