Why don't you start from the assumption that all available plugins are compatible with the latest version of core, then have a system whereby end users can submit error reports when they find an incompatibility with core? That would crowd-source compatibility testing across the user community instead of leaving it to the developer who may be long gone. It also gets round the issue of simple plugins that will almost always be compatible with future versions of core but that are in fact years old. I suppose what I'm describing is a kind of review system like Trip Advisor (http://www.tripadvisor.co.uk) for WordPress.
Taking the crowd-sourced compatibility testing idea a step further you could begin to build up a database of inter-plugin compatibility too.
As a side issue, I note some plugins have been given very similar names and names sometimes get abbreviated in the admin dashboard. There is no centralised reference system for plugins (and themes) to give each one a unique ID, so it can be hard to figure out that I'm looking at the same plugin in the admin dashboard as I found browsing wordpress.org.
If nothing else, having the "Compatible up to:" info in a column in the dashboard would save many a click. Maybe someone's could or already has written a plugin to provide that?