Two new returns (bidderFullName at #13 and ownerFullName at #15) have been added to GetAuctionItemInfo. Owner, previously #13, has been pushed to #14. Returns previously after owner (saleStatus, itemId, hasAllInfo) have been pushed forward by two places.
The full call signature is now name, texture, count, quality, canUse, level, levelColHeader, minBid, minIncrement, buyoutPrice, bidAmount, highBidder, bidderFullName, owner, ownerFullName, saleStatus, itemId, hasAllInfo = GetAuctionItemInfo("list", offset)
One new return (bgQueue pushed from #4 to #5) have been added to GetLFGRoleUpdate.
The full call signature is now inProgress, slots, members, category, lfgID, bgQueue = GetLFGRoleUpdate()
StartWarGame("target"[, area]) "target" unitid was unitName previously
GetUnitName(unitid[,showServer]) returns 'name-realm' instead of 'name - realm' (spaces removed) and most commands that accept a unitname now, work with 'name-server' format (/invite, /ginvite, /trade etc
A new return has been added to GetInstanceInfo - instanceGroupSize at #9 which gives the number of players that the raid's difficulty is tuned for (either the max players for normal raids, or the current number of players for flex raids)
Players from Connected Realms (5.4 feature) can be interacted with in more ways (e.g. trading) than players from Coalesced Realms (old cross-realm zone functionality). UnitRealmRelationship returns information about another player's realm.
A new error condition event, SAVED_VARIABLES_TOO_LARGE, was added which indicates that some, or all, of an AddOn's SavedVariables were not loaded due to the player's machine being out-of-memory.