Eh, Maybe. But I think 10.5.7 is just a week or two away, who knows how long Safari 4 will be in beta.Because the final Safari 4 will be out by time 10.5.7 is?
So one could assume that 10.5.8 and 10.5.9 will be released and then 10.6 Snow Leopard? Snow Leopard might not come out until at least Q4 '09 if that's the case.
Tiger was at 10.4.10 when Leopard came out, and Apple released 10.4.11 not too long after. So small updates are not really an indicator for the next OS release.