They can already steal cars 'remotely'. Apparently they come up to your car with some sort of box/laptop while a mate stands by your front door with a scanner. If your keys/card are close enough to the front door the scanner picks up the information, transmits it to the guy with the 'black box' who then deciphers the code, car doors open, crooks jump in and drive off. No key/card needed. Seen it on a crime video a short while ago. Someones home cctv caught them on film but I don't think the crooks got caught.
Obviously it will only work on modern cars. For those of us with old style ignition keys they would probably resort to traditional methods.