After having treatment for interstitial cystitis, will my bladder capacity return back to normal?

Yes. Usually with interstitial cystitis the symptoms of frequent urination occurs because the bladder wall is inflammed. Bladder capacity remains unchanged. Once treated you get symptomatic relief.
Is should improve. Your bladder capacity might not return to normal but it will likely improve. Symptoms such as frequency, urgency and pain should improve as well.

Related Questions

After going through treatment for interstitial cystitis, will my bladder capacity go back to normal?

IC. As the bladder regenerates and the inflammatory response stabilizes, the ability of the bladder to relax improves. The bladder becomes more flexible and the capacity improves.
Possibly. Provided your bladder muscle has not undergone fibrous change (like scar formation) in which case capacity can not return to normal. Milder cases of ic gan regain previous capacity especially if treatment includes bladder hydro-distension under general anesthesia. This has helped a number of my younger patients.

Is pelvic floor rehabilitation therapy effective for interstitial cystitis (aka: painful bladder syndrome)?

For symptoms yes. But it probably doesn't actually treat the condition ie heal the bladder wall. Painful bladder syndrome includes manythings that aren't ic such as pelvic floor dysfunction that will respond well to rehab.
YES. Many cases of ic or pbs are really problems of pelvic muscle and nerve dysfunction and not a bladder disease. Pelvic floor pt can be incredibly helpful.

What is the best treatment for interstitial cystitis that won't cause weight gain?

See your doctor. Problems like these can only be correctly handled by your doctor in person. He/she needs to listen to you, perform an examination and possibly run labs or other tests. That's the only way he/she can find out what's going on and what to do about it.

What are the symptoms if a person having interstitial cystitis or bladder cancer?

See below. These are two completely separate issues. Interstitial cystitis is continued pain and inflammation, suggestive of uti, but without evidence of uti. Bladder cancer is often silent, manifested only with unexplained blood in the urine. Bladder cancer is diagnosed by cystoscopy.
Depends. Interstitial cystitis is a diagnosis of exclusion. It causes suprapubic pain and a persistent, urgent need to urinate. Bladder cancer can cause no symptoms but often microscopic or gross hematuria (blood in urine).
IC. Interstitial cystitis has many symptoms similar to bacterial cystitis. Typically patients have urgency and frequency and even pain with urination. Pelvic pain and pain with sexual intercourse in women is also very common. Bladder cancer is quite unusual in your age group. I would not think this would be very high on the differential diagnosis.