Allowing SVG in <img>s is bad news. Many web applications differentiate <img> as fairly innocuous allowing it even from third parties, but not <object>, because <object> holds power.
SVG is incredibly powerful. It contains scripting, hyperlinks, <svg:image> even allows possibly third-party images to make HTTP requests. I also suspect that a fairly small SVG can DoS the renderer by requiring exponential time to render. That is a huge paradigm shift.
<img> tags would require a neutered implementation of SVG to match the security model of most sites, even more so than just dropping scripting and animation - it would need at least to disallow <svg:image> links to third and fourth parties, and have a render timeout.
I would recommend this is not fixed until that stuff can be thoroughly looked at.