FYI: This is mainly going to be a rebalance/bugfix patch. Expect both PvE rebalances now that the dust has settled on the Savage race and PvP rebalances as followup for all of the Frontlines adjustments.
The following content will not be coming until 6.45 sometime in late July/early August:
Blue Mage Update
Mount Rokkon (Variant and Criterion Dungeon)
New Hildibrand Quests
Next Relic Weapon Stage
Next Crafting/Gathering Relic Stage
The island sanctuary bug fix concerning the Workshop Board that was originally slated to come with 6.41 ended up arriving earlier as a hotfix, but there may be other fixes included in this patch that were not mentioned as part of the original 6.4 patch notes.