tl;dr: no, a flag's status will never change once it has been set.
There are three types of flag statuses:
Helpful means a mod specifically marked the flag as helpful, or the action that you were suggesting through a flag was taken by the community.
Declined means that a mod specifically declined the flag.
Disputed basically means neither happened. A mod never actually looked at the flag and declined it, but the action you suggested wasn't taken in response to the flag either. This can happen in any number of cases; certain flags are marked disputed when the post is edited; non-moderator users can choose not to act on a flag (either through the 10k tools page (which has since been removed) or through certain review queues) which disputes a flag, etc.
Note that any flag marked as "other" will be seen by a moderator, and no actions taken by any user will ever automatically resolve the flag, as such "other" flags cannot be marked as "disputed".
While having declined flags is bad, having disputed flags is...less so. They're certainly not something to be as concerned about, because it usually means someone wasn't specifically evaluating your flag, but rather performing some related action that rendered your flag "moot" in some way.
Declined flags will "count against you", but disputed flags won't; it's more like you never submitted them in the first place.
In generally I'd say don't be too too concerned. By all means look through your flags periodically; if you see declined flags then a trusted site moderator specifically felt that your flag was wrong, so you should consider reforming something. While a disputed flag might mean that you're not suggesting the proper action, it also might not. By all means look into it, but if you can see that you did the right thing (i.e. the post was later closed/deleted) then you know you're fine and move on.
Flag statuses are primarily just a form of feedback to you. So long as you know how to properly respond to similar instances in the future, everything is fine. If you have a particularly huge percentage of declined flags then you may enter the field of "flag abuse", resulting in some sort of consequences, but you'll almost never unintentionally get there. Beyond this feedback, the number isn't really used anywhere.