This could be a good move for Dan. Renault have been improving since reentering F1 and teams that build their own cars engine and chasis seem to do better. Red Bull have not been able to get past Mercedes or Ferrari these past years and they are ditching the Renault engine and moving to a Honda engine.
Williams won several wdcs with Renault engines. Renault are not a minor player nor a slouch in the f1 world. They bought Benneton around the turn of the century did quite well then changed the name to Renault and if we're going to invoke Alonso analogies, Alonso won his only two world championships with Renault, and none with Ferrari.
It will be an interesting season next year that we don't get to watch.