Remembering that there were lengthy posts on this forum predicting how WN would wreak havoc on DL in ATL, these changes confirm that DL is a fierce competitor and that WN's strategy is built around going for new markets, and only where necessary, competing with network carriers were it thinks it can succeed. ATL is just one more DL hub where WN has not significantly increased its market position and even in Florida where DL pulled back the most post 9/11, WN has not largely directly competed with DL.... ATL-Florida is the largest overlap between DL and WN and WN is pulling back even further.
Remember that WN's size at ATL will be almost 100 flights/day less than FL's peak... granted FL used smaller size aircraft (the 717s which DL is taking possession of) but WN's presence in ATL will be smaller.
WN will focus on the local market as has been predicted but they will find it very hard to gain a significant presence in the local market when DL has as much as 3X more capacity in many of the markets. And the number of markets that WN will serve from ATL will be smaller.
WN is a great airline but they know where and when to compete. ATL will be an important market for them but will be far from the size many said it would be when the FL merger was announced.