Numbers in the wild have fallen dramaticly ! : Ring-Tailed Lemur Populations Have Crashed by 95 Percent
The only ray of hope is that they do so well in zoos that they'd be easier to reintroduce - but the decline is shocking in speed and likely not the only species to drop so rapidly within that region
Small scale re-introductions are already occuring with confiscated pet ring-tailed lemurs... But this decline is really surprising especially given the relatively large area they until recently at least roamed... Fortunately they occur in several well protected (but not inter-connected) national parks / private reserves.
Another article about the dramatic status of the Ring-tailed lemur : Will Madagascar lose its most iconic primate?