Obviously the world could look a bit different by 2025, but my expectation is that the 757s stick around for a long time and they downgauge to lie-flat 757s.
Down-guaging to a 757 will only work on a handful of Int'l routes. The 757 can really only do TATL routes out of the Northeast. Anything beyond that and the 757 struggles on the range, especially in the winter.
I wonder if this announcement means a cancellation on the plans to put entertainment screens on the 717 since not long ago (pre-COVID), I'm pretty sure there was an announcement that the 717s would be getting seatback entertainment screens.
I'll be curious to see what DL's plans are going forward and to see if DL looks to try to leverage Boeing and Airbus against each other for perhaps an A321XLR versus 787-8 order (or if DL looks to pick up aircraft on the second hand market, such as some A330-200s) as a potential replacement option to maintain all/most of its current (pre-COVID) TATL and TPAC route map by 2025.