I interpret this as DS and 2DS games coming to Nintendo Switch Online at some point. Not terribly hard - just have the screens side-by-side, or rotate the Switch 90° for people who want the old experience.
It could even be like how Nintendo is doing the Game Boy last year, with basic Game Boy on the standard plan and GBA with the Expansion pack. Basic DS games would be on the general Online plan, and newer 2DS/3DS games with the Expansion Pack.
It could even be like how Nintendo is doing the Game Boy last year, with basic Game Boy on the standard plan and GBA with the Expansion pack. Basic DS games would be on the general Online plan, and newer 2DS/3DS games with the Expansion Pack.