You raise a truly terrifying specter--romance. Harry and Hermie sitting in a tree, K-I-S-S-I-N-G? Eight-year-olds around the world will turn queasy at the thought. Of course, we did get the first glimmerings of it in Chamber of Secrets, when Hermione--along with half the girls at Hogwarts and everybody's mom--go all dewy-eyed at the thought of Gilderoy Lockhart, that god-awful blowhard of a Defense Against the Dark Arts teacher, the one with the perfect profile. (Rowling, please! You're giving girlkind a bad name.) In Prisoner of Azkaban, there are hints that Harry's sweet on Cho Chang, who plays the same position he does on Ravenclaw's Quidditch team. She's a fourth year, which makes her an older woman. Then there's the littlest Weasley, Ginny, who conceives a crush on Harry early in Book 1. It gets her into trouble in Book 2--evidently, wanting to make a good impression on your beloved is another impulse that can inadvertently put you in the hands of darkness. Is there more story to be milked there? Ginny, for example, could turn into a knockout in Book 5, when she should be 14 or so, winning--too late--the hitherto impermeable heart of Potter, then extracting just revenge by scorning him utterly, sending him off on a quixotic love-quest just when he's most needed to save the world. No? I doubt it, too, but it's a thought. I'm more inclined to look for the sexpots of supernatural tradition: sirens, vampires, various enchantresses, those green ladies with rotten or serpentine lower bodies--what are they called?--who show up in (for example) Coleridge's "Christobel." Can you see Harry and his rival Malfoy vying for the attentions of a mermaid? Well, whatever Rowling does with sexuality, you can be sure it'll be funny.
We know that wizards date muggles, from time to time--I'm pretty sure some of the kids are products of mixed marriages. (Can't remember who, though.) That's an interesting idea--Rowling could bring in a young muggle hero. It needn't be a love interest; it could just be someone with whom frustrated readers lacking all magical talents can identify. Someone utterly unmagical who nevertheless enters the wizard world and makes a difference. I agree with you that we all know ourselves to be misunderstood magicians trapped in a horribly mundane world. (This is particularly true in childhood, but I'm not over it yet--are you?) Still, there's that nasty inner voice that revels in whispering words of reason, and I, for one, believe it, too--it makes a plausible case that you and I are ordinary people after all. So Rowling might do us a service by writing a place for us. (Well, me, anyway. You're clearly a real magician.)
I'll be astonished (though delighted) if any of the characters turn out to be gay. Bet you a silver sickle the homosexual themes are treated with sublimation and symbolism.
As far as Harry's being tempted by power, I see what you mean, but I don't really think that's where the series is headed. We've seen it so often before--Saruman in Lord of the Rings, Milton's irritating Satan, even Voldemort himself--and Harry isn't the type. He's too ordinary. Sure, he loves winning at Quidditch, but he's just not into power. Or fame, even, really--remember how grossed out he gets (as does the reader) when Gilderoy Lockhart gives him tips for grabbing the spotlight? I say his failings will be less about power, more about love. In The Sorcerer's Stone, he's tempted by a mirror that shows the viewer's heart's desire. Gazing in it, Harry sees his family for the first time: his dead mother and father and a whole array ancestors. He can hardly bring himself to turn away, and sneaks back for another fix whenever he gets the chance. I think he's more likely to be caught by that kind of temptation than by a hunger for power. Voldemort could pose as the guardian of Harry's heritage, as someone who loves him. But you could be right about Harry's anger towards his parents--they did leave him dramatically in the lurch, after all, despite saving his life. I'd sure be mad if I had to go live with that aunt, uncle, and cousin.
I'm looking forward to learning more about the four houses that make up the school. There are the ambitious Slytherins, the brainy Ravenclaws, the "just and loyal" Hufflepuffs, and the house with all our heroes, Gryffindor, "where dwell the brave at heart." It's not immediately clear why the Sorting Hat puts people in the houses it chooses. For example, wouldn't you guess scholarly Hermione would belong in Ravenclaw? And I'm still waiting to find out what's so brave about poor Neville Longbottom, who keeps losing his pet toad, getting scolded by his grandmother, and cowering in corridors. What's he doing in Griffindor? He does have a brave moment when he stands up to his friends--he thinks they're up to no good--but it's not quite enough. So far, we don't know many Ravenclaws or Hufflepuffs. I'd like to see a book in which Rowling calls upon the strengths of each house--even Slytherin--to aid Harry in his epic struggle.
What would you like to see? Got any suggestions for the divine enchantress?