it's good news indeed, because they only extend the medicals if it's the only thing preventing them from issuing the visa... so you're near the end! difficult to say how long it takes, but at least in your case they have been pro-active, as your meds are expiring in 10 days, and they have asked for the extension... it's difficult to know how long it takes. I would "guestimate" that your PR should be issued in a month, or less... maybe 2 more weeks for them to get the medical extension back (depending on when they asked for it), and maybe 2 weeks to get everything together. but of course - it's only a guestimate...
Good luck,
Sweden