He cant but the mist form will break the TK, so when Kain goes solid he can start his attack again, you just mentioned Tk and I told you the counter. Teleport or mist, mist form can be attained almost instantly in a second and takes just as long to return back to physical Kain.
Also I wonder if Kain can turn his opponents into mist, it would be quite funny to have Ganon turn into mist and be swept away on the wind....