The one reason why Warcraft's movie didn't do too well was because of the plot that was attempted to be made simple but came out with too many unexplained plot points. this is because Warcraft lore is too vast to be shoved into a 1hr 40 min movie.
But a live or Animated TV series would be the most efficient way of telling Warcraft's lore in a way that would make a lot more sense to the non-fan audience and also appeal to the fanbase.
The series could be closely canonical, direct continuation of the movie or a timeskip after those events if Duncan Jones and LegendaryPictures are down for it. (Warcraft 2 & 3 being told in a tv series rather than a movie sequel)
Considering they can take all the time to explain the lore, it can draw out into multiple seasons and character arcs. (Varian, Thrall, Arthas, etc) The possibilities are literally endless depending on where they want to end the series.
Though the CGI production cost for the orcs and stuff could be very costly. So it would be wise to start the first season with minimal CGI,(if it starts from Warcraft2, then the only ones that'd need CGI would be Thrall and Orgrim, Stormwind, etc) that way, if the season receives good publicity, they can then gradually step up the CGI and go crazy.
I feel like if they played their cards right, a Warcraft TV series could be very successful.