Sure it does. As another poster posted, to use the benefits earned. Beyond that, not much as changed if ones flying plans are going to continue their current ones.

2014 fly 125,000 miles and get the MQDs. Quite flying Delta and get Gold status on UA.

2015 DM all year on DL and Gold on UA. But the travel year is slow. But spending is still high enough. 2016 GM on DL and nothing on UA.

OR

2014 fly 200,000 on Delta. 2015 Rollover 75,000 miles and fly enough to be GM again and you are DM again for 2016. Or maybe PM again if you don't spend enough.