If they believe that you stole from their store, they will turn your plate information over to the police and you could end up getting a citation and having to appear in court
to fight these charges. This doesn't mean they have a good case. In order to convict you, the state would have to prove that you took failed to pay for goods you consumed, and they'd have to prove it beyond a reasonable doubt. That might be hard for them to do.
To arrest you and charge you, on the other hand, the state only needs probable cause
. That's a much, much lower standard, and frankly anybody can get somebody arrest if they've a mind to do it. Probable cause is only a reasonable belief that a crime may have been
committed and that you may have had
something to do with it. The word of a store security guard that they don't see you paying for food you've consumed, that they've been keeping an eye on you for that reason, and that you do not show them receipts when they ask may be enough to start the ball rolling. You will know soon enough.
Meanwhile, since they clearly know who you are, are watching you, and now have your license plates as well to alert them that you're in the store, you probably should consider shopping elsewhere, or hanging onto your receipts. You can, of course, stand on principle, but so can they.