This code renames the windows using one keypress and works fine for me. Haven't tested the 5 WoW version as I only have 2 accounts but it should work.

2 WoWs:

Code:
<Hotkey ScrollLockOn Ctrl R>    
    <SendPC local>
        <RenameWin "World of Warcraft" HiddenDialog>
        <RenameWin "World of Warcraft" HiddenDialog>
        <RenameWin "World of Warcraft" WoW1>
        <RenameWin "World of Warcraft" WoW2>
5 WoWs:

Code:
<Hotkey ScrollLockOn Ctrl R>
    <SendPC local>
        <RenameWin "World of Warcraft" HiddenDialog>
        <RenameWin "World of Warcraft" HiddenDialog>
        <RenameWin "World of Warcraft" HiddenDialog>
        <RenameWin "World of Warcraft" HiddenDialog>
        <RenameWin "World of Warcraft" HiddenDialog>

        <RenameWin "World of Warcraft" WoW1>
        <RenameWin "World of Warcraft" WoW2>
        <RenameWin "World of Warcraft" WoW3>
        <RenameWin "World of Warcraft" WoW4>
        <RenameWin "World of Warcraft" WoW5>
It may be beneficial to split it into separate keypresses as well in case you need to open a new WoW after a crash or something.