Miqo'te being only female only initially, and for that matter roegadyn and highlander hyur being male only initially was a result of basing those races directly on FFXI's races which also had those gender limitations. And the reasons for those limitations were technical - FFXI's PS2/DX 8 client could only store enough data for four character races, until Tanaka realized they could actually create a fifth race, but a single gender one, if they made one of the four a single gender also.
Hence in FFXI mithra have always been female only and galka male (although a single male mithra npc did appear in the game eventually, it was handwaved that the males are rare and usually kept in the home raising the children, and galka... were written into the lore that they actually reincarnated at the end of their lives into a new form Doctor Who style and didn't even have an actual gender, but were for all intents and purposes were considered 'male'.).
Because Tanaka wanted FFXIV 1.0 to be a spiritual (and initially, literal) successor to FFXI, including the briefly entertained idea of moving all existing FFXI player data into FFXIV 1.0, similar races needed to be used, and thus the gender restriction for miqo'te and roegadyn - they needed to be single race to match up with the planned transfer of FFXI player data as well as give something familar to encourage FFXI players to migrate to the new game when that idea was quickly found to be unworkable. Male highlander hyur being restricted though is still a big question mark - maybe they just ran out of time and didn't get around to adding female models and didn't even bother handwaving it (1.0's development was famously a mess after all).
Either way, as others have mentioned they probably just haven't gotten to finishing off male viera yet, as well as wanting to save it for the Japanese Fanfest next month - have patience and keep the faith a little longer!![]()