It’s apparently been available since Feb. 29 but little was said about it and no one is quite sure what the maintenance updates are about.
The only item I found that was fairly certain was that a dictionary does not have to be ‘set’ again as was needed often when you re-set the Kindle Touch.
My Kindle Touch is still at v5.0.3 and the ‘Update your Kindle” button is grayed out. I’ll be updating instead of waiting, although the latter will be easier for most. There is usually no functionality change in a maintenance update.
I recommend that most wait for it to happen unless they need to have it now and haven’t been updated yet. See further below on that.