Talk about a slightly necroed thread. . .
As someone who wore recreationally for about a year . . .and may soon be wearing more often due to a legitimate issue (read the blog I just posted.), I would definitely agree that you do lose a bit of control and will have an accident if you are not vigilant, but you will more than likely be able to regain control with time.
This loss of control is in fact incontinence. . .it is a symptom, not an underlying condition. If you wear a diaper for a long period of time, you will become accustomed to just letting go when you need to, and may not think about it when you are not wearing diapers. I would call this a form of functional incontinence, similar to that of a baby or child who just does not know better or think to go to the bathroom. Start listening and reacting to the signals again, and you will be fine.
Also, if you never hold back your urine, as in as soon as you need to you are letting it out, your bladder will never be full, and will shrink with time. This will be very gradual and could take years to have any real effect. When you are then not wearing a diaper, you will find that you need to urinate frequently because your bladder is smaller. This can lead to urge incontinence, or the sudden need/feeling to urinate with little time before you overflow and start leaking. Simply stretch the bladder gradually by holding it for as long as you can, but never letting it become painful.
In both cases, your muscles should be just fine, just need to get used to using them again, so it is not a permanent loss of control.