A great observation by Search Engine Watch clocked a new SERP on desktop that shows card-based search results, separating out each result into its own area of the page.
The most significant part of this experiment (to me, because I called this months ago) is "The snippet width is significantly longer on the card-based SERP. There are roughly 20 extra characters here than on the standard width."
When Google rolled out wider ads and removed the right-hand rail ads back in February, I postulated that we'd see wider organic SERPs listings to maximise the available space.
This appears to be the case and we should see a wider rollout if testing appears successful.
What's interesting on these results is that none of them contain adverts so it'll be interesting to see how Google gauges the impact of this new format: it's not as though boosting organic CTR in a SERP containing adverts is in their interest...
It seems Google is once again experimenting with a card-based SERP for desktop, where each result is placed in its own separated box like you would normally see on a mobile search.