Hi. Here's what I posted on Fleet back when it was first announced:
At this point I (and other JetBrains plugin developers) am waiting for them to provide a formal plugin SDK. They are committed to doing so, but at this point it's still too early in the product development cycle for them to make it available.
The general thoughts in the posting linked above still hold, though. My guess is that the Fleet integration will be a subset of what's available in the full version of Illuminated Cloud 2 simply because of a more narrow set of plugin extensibility points.
So unfortunately I can't really speak about timing or content for such an integration, but I do plan to support Fleet in some manner once it's viable to do so.
Regards,
Scott Wells