I thought this was an interesting development after the three tabs Gmail implemented. It should be noted that marketers have already found a 'trick' to get Google to keep reloading a web pixel bug by serving no content so they can track open rates. But, IP addresses and, thus, geo-location of recipients is now invisible to marketers. And the images will load faster within Gmail for folks who choose to display them.
I don't know why a tinfoil hat would be required to speculate here. As with the cookie proposal, this potentially puts Google into a position where they can profit by further intermediating between the marketer and their target. Or if you prefer, they can help safeguard the privacy of their email users.