Yesterday it was announced among other things, that there would be a special Supergirl and Flash musical crossover. This makes a lot of sense since you have some extremely talented singers with both Melissa Benoist and Grant Gustin coming from Glee and Victor Garber and Jesse L Martin having Broadway backgrounds.
But now the Hashtag Show is saying that Joss Whedon will be coming on board to direct. Whedon put together an all singing episode of Buffy the Vampire Slayer called Once More, With Feeling and of course was behind the Doctor Horrible Sing-Along Blog. Along with the Whedon speculation, they claim that the villain will be The Music Meister and they figure we will see Neil Patrick Harris in the role.
It would be huge news to see the former Avengers director step into the DC TV universe, but it does sound like something right up his alley. But there is no confirmation from the CW and you'd think a 'get' as big as this would've been announced during their presentation at the TCA yesterday. So using Rich's old traffic light rating system, I'd call this one a red light for now.