Naturalization process question

I have a question regarding my natrulation process

I submitted my application - marriage based back in March and had my interview on Sep 15, everything went well, the visa officer said that my case is straight forward, but he mentioned that he need to get some paper work from another office, so that he can not give official approval now, however, I should get my citizenship by Thanksgiving.
 

So in my N652 notice, it says that I have passed the tests and USCIS will send me a written decision about my application. As of today, almost a month has passed and I still have not receive my oath notice. (Is it normal to wait that long?)
 

The issue is that my parents I94 expires Jan 4th and the original plan is that I will file I130 and I485 for them before their I94 experiences, so that they can stay here.

Should I be concerned that I will not have enough time and should file my parents I94 extension, my parents have been staying in US for pretty extensive time, every time 6 month, should I be concerned that the extension will not be guaranteed and also if extension is guaranteed will their be any negative implication on their future visa application, etc.
 

Thanks a lot for your advise and help as always.