The arguments for Adding Male Viera/Female Hrothgar:
More Character Variety - Adding visual variety to the game to seem more robust and diverse
Parity in gender selections - There will be a female/male equivilant to all races
Letting people have the avatar they want - Customization people want when it comes to their player avatars
Arguments against:
Time/Money Budget Concerns - This would take away from them developing other content.
Lore - Lore stipulates that Male Viera are reclusive (There is no lore regarding female hrothgar at the present.)
Ill start by pulling apart the lore angle, since that is probably the weakest of the arguments against. Lore is not a concrete facet of any game. We can all agree that changing lore can break a game, so it has to be done carefully. However, the lore regarding Male Viera within FFXIV is incredibly sparse, and is (at best) just a reiteration of lore from separate final fantasy games. As it stands, FFXIV is not connected to any other FF in an official capacity. It only borrows elements from other FFs, which is a fairly consistent trait of FF games in general, and not indicative of them being linked. It's like if someone wrote fantasy stories that used similar elements (Dragons, dwarves, elves) it doesnt mean those stories take place in the same universe. Until the devs specifically say FFXIV is connected to other games and is not paying homages or non canonical cross overs for player fun (rather than lore), the lore regarding male viera is easily up for change. Particularly, as said, its very sparse and not really well put together in this case. Remember, Lore is in service of Gameplay, not the other way around. If your lore limits player options for conceivably arbitrary reasons (particularly when you retconned similar lore in the past for gameplay - see male miqote/female highlander/roe) then its not good lore. It's an excuse, not a world building facet, and people see through it typically.
We can also point out there is no real lore reason for no female Hrothgar at this time, so this hurts the "In Game Lore" argument.
The money/time option is a better argument to have. Yes, developing the opposite sex will end up consuming resources. However, much like glamour, or holiday events, or etc, all these things add flavor to the game and require time and effort. We have no way, as a player base, of quantifying how much time and effort is required to make the opposite sex here. Nor do we know how that effort will impact other content. It may very well be that the impact would be 1 less glamour item, emote, or housing item over a content patch, with no effect on primary content (MSQ, Raid, Savage). We can only speculate. Furthermore, while a few people may not like this, races with genders is content. Its a facet of the game that some people tune in for. We can all agree that if we were all giant green squares, that the interest in the game would be reduced. Part of what makes the game interesting for players is how their character looks. It matters to a lot of players, and is not an arbitrary thing. It's also an income method for SE (as people do Fantasia). The position that "It's not important to me, therefore SE shouldnt make them" is fundamentally the same argument that can be used against any content of interest. There are people, as an example, who dont care about the Nier Crossover raid, and would rather have both sexes in game. Point is, if the reason to reject it is out of personal subjective preference, then dont be surprised if that can be turned on its head against content you want.
Honestly, I dont think either argument is particularly great for not adding them. We have precedence in game regarding genders, there does appear to be a large desire from the player base, SE was very quick to say "Were gonna look at player feedback regarding this" (probably cause of the audible sighs of disappointment from the audience in FF Japan, among the forums blowing up here). They were on a shortened schedule to make sure ShB gets out on time, and they gambled with an idea they thought would make more people happy. I dont think it particularly worked out like they hoped. If they didnt think they would have resources going forward, they wouldnt have even mentioned "watching feedback" as that would probably hurt them harder long run and damage the SE brand. It's more likely at this point not an IF but a WHEN we get them as itll just be something developed slowly overtime (possibly released for the next xpac.) Who knows though, as I was wrong already, thinking SE would do the smart thing and release male Viera.