OH DEFINETLY. The show was never in jeopardy of being cancelled. I would cry if the show got cancelled and we never got to find out the REAL mother. SEASON 5 will def. air :D chyeahhhh !
link sualey posted the confirmation here. it WAS on the bubble for a while (remember s3? before the strike?)- but yeah this time the ratings were so good there was less chance of it being cancelled!
Yes, there is going to be a 5th season. Read it here: link
though I didn't read the whole thing but if I read the right place there is gonna be a next season! :D