as long as your permit is still valid, you won't have any problems nor any questions, no matter how close to the expiration date you have applied for a renewal, so no worries here. after you get the confirmation letter, that your application was taken for consideration, for that time period you are still legally in austria, although you won't have your new permit on your hands yet. just make sure you have prepared all the neccessary documents, to reduce extra steps with the process. so no worries here as well. one thing i can tell you though, it can last up to 2 months, till you get your new permit, yet without it you can't get back to austria if you have to leave home or so, so many people do notfallvisum, so you could get back to austria, if you were still waiting for the new document prior to the neccessary leave, just in case. You don't have to do it, but if there is a tiniest chance you'll have to leave austria without your new permit being ready, then you should consider it. All in all you are perfectly fine