It's possible that the USGS server has historical aerials on it. It does have historical topo's. I can have a look. But yes, the current/old server is going away, so we will no longer have access to those tiles.
The new topo's (also from USGS) are the same scans as the current 'topo' layer from everything I have seen. Only downside is that there are a few gaps in coverage (such as the Tucson Mountains, where I live!).