A few sources are discussing the possibility of an update to WP8 (Apollo) to Apollo+, two notable ones below:
TheVerge says there are various fixes, including WiFi and audio and implement new things for WP such as VPN support. It was noted that, (as important as it was to get it right out of the bat) Microsoft ran out of time (Well done MS) on a number of features (such as a rumoured central notification other than homescreen tiles/lockscreen). On the upside, there’s plenty to like about WP8 and it’s super stable for me. I’d rather than than the possibility of a notification centre and something buggy (but then again, who says we shouldn’t have had both?
It’s noted that Apollo+ isn’t going to be a big update like WP7 to WP7.5 perhaps but more of an update to push fixes and features (like the mini updates WP7.5 received to get features such as WiFi tethering).
Apollo+ will also test OTA updates (previously not possible)