What if they do make Murlocs playable and in tandem, make the toy free?
Nope. You got a Murloc costume when you did the quests to go into that one cave and kill a lobster guy.
The costume made you friendly to all the Murlocs on the beach. It had a hilarious jump animation and its own dance!
I’m guessing never, because the fact that the toy exists at all is likely a direct confirmation that they have no intentions to ever make them anything more than gag NPCs. They saw the two decades of requests for murlocs but knew that the race lacks many of the things that existing playable races have, like racial leaders, capital cities, intelligible speech, etc., so they made them playable through a toy and essentially told everyone asking for them to shut up.
Playable Murlocs eh? Well, we’ll add it to the pile. Tosses a Murloc plushie onto the pile of other races people want
There’s a Murloc that can speak Common and Alexstrasza also displays her ability to speak and understand the Murloc language in one quest. 
if we get playable Murlocks
I DEMAND WE GET PLAYABLE GNOLLS, I WANT TO BE A WILD CRAZY HYENA PERSON HELL BET ON DESTRUCTION LIKE A HEAVYMETAL MANIAC.
i need playable Gnolls!