I'm not sure if anyone's mentioned this yet, but I think Kakashi can counter this
If Tobi tried to warp Kakashi away, he could counter by warping Tobi's head away with Kamui. Since warping something away is proportional to the size of the object, Kakashi would take Tobi's smaller head off with Kamui before Tobi could warp away his entire body. I know Tobi said that Kamui doesn't affect him, but I'm assuming that he was referring to the fact that he could immediately become intangible before Kakashi could hit him. If Tobi tried warping away Kakashi, he would be tangible and therefore Kakashi could actually hit him