I got a comment today on the updated "Masters" pic that expressed an attitude I've seen from a small minority of fans this last week- that they liked Missy, but hoped it would somehow turn out to not be a "natural" regeneration, or that they'd be upset if some reason wasn't given for the change in an established character's gender. They equated this to frustration with Thor's recent sex change- which... to go on a tangent for a sec... is odd since the hammer just got handed to someone else. It's not like the blond male individual we usually think of as "Thor" suddenly personally transformed into say... a frog. And where was the outrage against Beta Ray Bill in the 80s (we all know Walter Simonson has a secret pro-alien agenda)??? They also compared it to Green Lantern Alan Scott being "reimagined" as gay (and he was definitely straight before, b/c god knows a gay man in 1940s America would absolutely let everyone know about it if he was). But at least they didn't use the old chestnut "Why not just make James Bond a woman too?", as if Bond was also an alien who could spontaneously regenerate every cell in his/her body (though if he was, Sean Connery suddenly bursting into flame and morphing into George Lazenby is waaaaay more of a stretch than John Simm turning into Michelle Gomez).
But here's what my response was, cut-and-pasted with minor changes...
It's weird how many people draw a line on what is "too much" for regeneration, and it probably says more about them than the agenda of any writer working on the show. I'm not saying that as a high-and-mighty attack, b/c I have a "too much" threshold myself. I'm fine with a spontaneous female regeneration out of the blue, but an American accent on the Doctor would drive me up the wall b/c I think that says more about the Doctor's mind than any external physical change. This is a highly stupid attitude, b/c we've already seen him go Scottish (twice), Cockney, Northern, shift from posh to working class... why are those acceptable and not American, when he isn't even from Earth? Is an Australian accent more acceptable b/c it's more Commonwealth-y? How about South African?
It's completely arbitrary, and has everything to do with our hang-ups, and nothing to do with a thousands-years-old alien who periodically sets fire to every cell in their body and becomes a completely new being. As far as the question of "should the writers go there?" I guess it's a question of how willing we are to have those hang-ups challenged when we're dealing with the Doctor's alien-ness. But is a gender change really even that alien still when species right here on Earth do it naturally? en.wikipedia.org/wiki/Sex_chan… And when humans have been having transsexual surgery for the better part of a century, and "gender identity" is a more discussed topic than ever, delving into this territory would maybe make Time Lords MORE relatable to many members of the audience.
But rationalizing it "in universe"... Time Lords had a billion years of evolution and history- so who knows where they'd be with these issues in relation to us. We don't even really know if their language has gender pronouns or if this is something the TARDIS translates for us (Missy made a Lord/ Lady distinction Saturday, but that could just be her speaking English and relishing the cultural quirks of us Earth types). Did Susan really call the Doctor "Grandfather", or is that just how the TARDIS explained it to us?
As far as Time Lord characters being "established" as one gender or another- actually very few are on TV. Best I can remember, we've only seen or heard of seven Time Lords in multiple incarnations, and they break down like this:
The Doctor (presumably all regenerations seen on screen): always portrayed as male, though interestingly "Night of the Doctor" seemed to imply a gender switch was roughly equitable with a change like "young or old" or "fat or thin"
The Master (only a small percentage of "natural" incarnations seen on screen): mixed
Romana (presumably all TV canon incarnations seen on screen): always portrayed as female
Rassilon (only a small percentage of incarnations seen on screen): only seen as a male
Borusa (only a small percentage of incarnations seen on screen): only seen as a male on TV (one major tie-in novel casts some doubt on whether this was always the case- but we won't count non-TV sources here)
River (presumably all regenerations known- but only three incarnations exist): always female.
The Corsair (no incarnations appear onscreen, only referred to): mixed.
So we don't really have much data to go on for how unusual this is, statistically- it may be a relatively common occurrence. It may be that some Time Lords "swing" one way or another more often than not, while some are more evenly divided. And again, bringing it back down to human terms- people having a late awakening with sexual orientation does happen (I know at least one person in my personal life who went through that in their late 50s). And again- it may just not be that big a deal to Time Lords. It might be about as important as always having a nagging urge to be ginger, and never QUITE getting it one regeneration after another. And then one day it happens, and it's a big deal for about two minutes and then we move on.
We'll probably know more about this Saturday. All we know for now is that the show is trying something new and challenging, and we should probably be happy that that's still possible after 51 years.