According to mozillaZine Firefox 1.5.0.5 Final is scheduled to be released today (and Thunderbird 1.5.0.5 the day after tomorrow). This will be most likely the last update that version 1.5 will see before the release of version 2.0.
Quote -
According to the Firefox 1.5.0.5 schedule, the planned release dates for Firefox 1.5.0.5 and Thunderbird 1.5.0.5 are Tuesday 25th July and Thursday 27th July respectively. All users will be encouraged to update to these maintenance releases, which will include security and stability updates but no new features.
And it seems that this is correct. Everything looks ready for the release.
The Release Notes page is ready. (link)
The release folder is on the FTP and it already has the update versions (link) (Freeware)