@tgray I just got my 2013 15” rMBP battery replaced for swelling. It only cost me $200, out of warranty, and it is like a new machine again. I would look into that option if you aren’t dead set on an upgrade.
@tgray Yes. Apple did the replacement. I brought my machine to the Apple Store and they knew just what to do. They shipped it out to an Apple-authorized service center, and I got it back in 3-4 days. You might want to do it anyway, even if you upgrade, to have a spare device, or to prepare it for sale.
@tgray Apple recently announced a recall program for that model. Check your serial number. //@@mjdescy