Official comment
We're unlikely to introduce more features around email opens.
Email opens have not been reliable for quite a while now due to the way browsers and email programs are treating the tracking pixel. Browsers and email programs block the pixel routinely, and then some security programs click the pixel to ensure it's OK before the email is read. The result is a stat that isn't as reliable as it once was.
Clicks are reliable and still tracked accurately. Total engagement, measured by the "Last Activity" field in Ontraport, is an even better measurement of your audience's engagement.