Visa and Study permit consultation

Hi,
I am international MSc student in UoA. I have the following situation
My study permit will expire by September 2012
My entry visa (on my passport) is already expired.

I will finish my MSc by December 2011 and start directly PhD by January 2012. I knew from CIC that the MSc study permit can work as it is issued for post-secondary studies in university of Alberta. The point now is that I want to travel to my home country by May 2012 and I need to issue an entry visa before I leave Canada. I have many options and I will be grateful if you provided me with your experience.
I think the options I have are:
- I can for now send my passport to issue an entry visa on my passport based on the study permit I already have. Will the new visa expire by the expiry date of the study permit (September 2012)? Is it OK in that case to reenter Canada in July 2012 with a visa and study permit that will expire after 2 month?
- The other option is to wait to January 2012 and get my unconditional PhD offer and apply for extension for the study permit then apply for a reentry visa. Is it Ok to apply for extension very early (in January while the permit will expire in September)? The problem here is the processing time. I heard from friends that if I issued study permit extension with off-campus work permit the processing time will be 1 month only instead of three, is it true?

I really appreciate your help and sorry for this long story.