I'm in a similar situation but with inland spousal sponsorship. I was under the impression that the Approval in Principal to Permanenet Residence status should only take a few weeks, but apparently this could now be nine months. Sadly, under this impression, we bought flights to the UK for xmas and intended to go travelling in asia for our honeymoon....luckily we didn't commit to flights there!
I called the call centre on friday and I was advised that the only way my application would be affected would be if I were to be refused entry to Canada on my return. Basically I didn't get an answer to the question of not being in Canada while my application was processed. I think we've decided to return home for xmas but then come back to canada in mid january, I think being away for months wouldn't be a good idea. Its reasonable that we should spend xmas with my family as i haven't seen most of them for 18 months!
Basically I think if you take your Work Permit and Visitor permit to show immigration on your return, you shouldn't have a problem. Call the call centre, at least then you're getting advice from the right source.....
I'm in a similar predicament. We sent our spousal sponsorship away the beg. of May...but it doesnt look like we'll be approved in time for our trip at the end of January. His work visa expired in May so we dont even have that to show. All I have is the reciept from our payment....they should have a form or something you can obtain saying you are going through the process. It's very frustrating!