She already is going to be a gay female lead. ND have confirmed she is the lead character for TLoU part 2. She also had a romantic interest in Left Behind. None of that is canon, it all happened and is still part of the world's history.
The bulk of what people are asking for was already on display in the first game (and for any haters, check those glorious game of the year awards), so I assume given the topic title some are just saying what next? Well, she is the lead role now rather than a secondary role from the first game.
I don't think anyone wants some ham-fisted Mass Effect sex scene for a token gesture that gay people have sex. While I'm being facetious there, yes, some games handle relationships like 14 year olds discovering sex for the first time. The games tone has been stated to be darker and the trailer inspired an Ellie who has seen some shit and is probably going partly insane. So for example is it going to be easy to fit in a Left Behind like more relaxed segment? Possibly, but Druckmann has pre warned this will be a darker game.
Given that it is a set world and is following on an already fairly dark ending to the first game there is a bit of advice for some thinking this game has some free role to be whatever they want it to be, to be brought back down to reality. Part 2 has very little chance of being a love story. It's most likely going to be a revenge story given the trailer and what Druckmann has stated. It also already does star a lead female gay character. Ellie isn't being rewritten, she's just aged and obviously we're going to find out how she reacts to Joel lying and whatever ends up happening to Joel. Whether she kills him, someone else kills him, or he's alive but Ellie just hates him for how he ended the first game. As I said, it's going to be a story of despair. It doesn't have a free reign to chuck the story from the first out of the window and write some happy days stylized drama. This is a dark, fucked up post apocalyptic world and while characters can display positive and happy emotions it's largely not what the canvas is there to do in the TLoU world. Hence politely and respectfully some people maybe need some expectations in check as the absolute majority of the sequel is probably going to be grim.