Worth waiting forever if it is a Freehold, since time is on his/her side.
If not, situation will become like what has been reported here:
https://www.facebook.com/assi.ak.9
"Simeon Kong: Normally Gov will avoid questions what to do when the tenures expired for public housing.....but not in Singapore. My friend’s HDB is now finding it hard to sell even though it has a good location as it is a 45 years old flat."