Just my thoughts, If Ayumi releases another single or if she doesn't, if she loses her #1 streak or if she keeps it. Does it really matter?
Look at the changing CD sales, even if she released 50 more singles over the next 10~15 years and they all peaked at #1 the sales will become less and less on the first week. Avex will just strategically release them on a week against weaker artists. I don't want Ayumi to keep her #1 streak by attacking artists weaker than her. I want an authentic number one against fair competition. Which may not happen anymore sadly.
Chances of another artist coming along and gaining 25+ #1's by physical CD sales are very unlikely as it's a good possibility the physical CD will be almost irrelevant in the next 10~15 years. Look at it's decline over the past 10~15 years as it is. Let's face it groups/artists like AKB48 are hyped up to be awesome and even they are starting to fall back some in sales/power. Ayumi has nothing to worry about for the overall of the situation.