If you read other comments, a number of people have done the trivial test and confirmed that images aren't requested until you open the email.
Re:Images Now Showing in Gmail
by staticfish on Thursday December 12, 2013 @03:27PM
(#6896967)
Wow this is really dreadful.
It will protect you from it being as a read receipt if (and I'm not sure if this is the case, though it should be trivial to test by sending email with images served from a site you control to an email you control without opening it) Google requests the image once it has received the email.