Is Ema's Skye theme in it from PWAA Case 5?

yes; a remixed version of it is in the game.

which tells you stuff like present wine bottle at statement 3 or something

If we get a detailed walkthrough from Croik (Possibly with help from Naila and Onamadia), you could. But it would be up to you tho.

Is Ema just a side character, or does she actively factor much into the story?

Dunno if this is actually a spoiler, but what is Broom Lady's first and last name?

I have been hearing things like in that case seven years ago( Which happens in case four) with phoenix's fiasco that had him resigned involed a genius he knew died. This isn't Edgeworth is it?!?!

How does GS4 use the ds ? Is it like anything in case 5 in GS1

From what I've gathered, she has pretty much the same role as Detective Gumshoe in GS1-3.

Yeah, it's pretty much on par with Case 5. I know there's fingerprinting, footprint taking and evidence examination, but if you're that interested I could dig around a litlle and get a proper list for you...
There are also two new features, the Minuki System and SUPER SECRET SPOILERY SYSTEM as well.

What role DOES Gumshoe play? Does he just show up in the flashback case, or does he have a role in the present?

Nope- poor old has no role in the present.

To any of the japanese readers...

Are the rumors true that Gumshoe quit after that case 7 years ago?

He does indeed quit the force

Okay, I know that Garyuu is his mentor, so I take it that he works at Garyuu's law firm, correct? So when Garyuu is convicted, who does the firm go too? Orodoki?

Poor Odoroki is out of a job after the first trial. He doesn't get the firm.

Does he start his own firm(with only one case udner his belt) or mayeb work at anotehr firm(Grossberg is the only one I can think of)?

I believe he goes to work with the Wrights (Nick and Minuki).

Yes.

What are all the characters from the previous PW games that makes an appearance in this game?

His "urk" face is rather underwelming, but he does have one.

since theoretically its odoroki who you play as,
what will the title of the game be be in English, (since it can no longer be PW, cos Phoenix is no longer the protagonist)?
will it be
"Odoroki (I forgot this part): Ace Attorney"?

*English name for Odoroki*: Ace Attorney

Okay, if Odoroki works in Phoenix's Law Firm after the first case, what's Wright & Co been doing for the past seven years? It's pretty clear that only Phoenix works there and considering he's been disbarred I doubt he would keep a law firm running for 7 years without any lawyers...

Phoenix, Ema, Director Hotti, The Judge, Payne, Gumshoe, and Meekins

Wright and Co. might have been loaned out to Kirihoto (i think thats spelled right), after the events of the first case, Kirihoto "gives" it back to Phoenix, also, the name possibly changed, and was loaned out to someone else...
possibly.
good question though.

What happens to Minuki and Odoroki's mom?

More distance, closer to traditional rivals--though not quite that either. Kyouya kind of bothers Odoroki. Kyouya likes to tease Odoroki (calls him Odeko-kun, which is "Forehead [-kun]") Kyouya is also helpful to him, though.

Ema isn't so much incompetent as she is unmotivated.

Yeah, like musouka said, whereas Gumshoe was passionate yet totally incompetent, Ema knows what she's doing but doesn't really care for her job.

The passionate question burning red: Where does Kyouya take Odoroki in what I assume is case 2? [We saw him saying "Come with me" or something in a screenshot]

He's actually talking to Minuki, telling her he will take her to the crime scene since they were technically authorized to be there. The background in the screenshot is not where that dialogue actually takes place in the game.