Michael's Favorites reported on their Winx Club news page about a bunch of new lines from Jakks coming out this year (including Mythix)
, but more relevant to the discussion is that we finally have an explanation for why, after the previous announcement of Tecna and Musa Harmonix dolls being retailer exclusives and said dolls even being featured as part of the TV ad
for the line, said dolls ended up never being released (at least in the US and Canada), in the form of an official response from Jakks:
"Musa and Tecna will not be released in Harmonix. Due to product wave strategies and high inventory levels prohibited the release of those two characters for the Harmonix collection. Once the retailers finally got through their high inventory they moved on to the next wave." (Source)
(Meanwhile, Witty Toys did make Harmonix dolls of those characters... Here's a vid review of a Tecna Harmonix.