I just updated a blog from 3.7.1 (with MP6 plugin v2.2.1 installed) to WP 3.8
Just a couple of notes on the behaviour:
The Core upgrade went smoothly.
On returning to view the plugins list afterwards, MP6 is still there but has now been disabled. WP tells me that there's an update (v2.3 from v2.2.1) ready for MP6.
As it was just a test blog (that doesn't matter if it breaks) I clicked on upgrade plugin. I'm not sure if my CHMOD permissions were wrong but I got this message (and then the plugin disappeared from my plugins list)
Downloading update from https://downloads.wordpress.org/plugin/mp6.zip…
Unpacking the update…
Installing the latest version…
Removing the old version of the plugin…
Could not create directory. /public_html/wp-content/plugins/mp6/
Plugin update failed.
the /mp6/ folder still exists in the plugins folder but it is no longer listed within the WP dashboard plugins list (of course MP6 is now part of WP3.8 so I guess this was to be expected)
I will now just manually delete the /mp6/ folder via FTP