There's been some info coming out about Katie Cassidy over the last couple months anyway. Common consensus seems to be she's a real piece of work, and won't be in the show much longer. That's why they've bought in Black Canary as a different person, and that's why Felicity is being bought forward more. They'll get rid of Laurel soon enough. Whether she goes away and comes back recasted, or just gets killed off, who knows.
If you follow any of them on twitter you'll see that Stephen Amell, Willa Holland, Emily Bett Rickards, and Colton Haynes all get on really well and hang out together, but you never hear or see anything of them with Katie Cassidy.
It's a shame, because Laurel (Dinah...) could be a cool character, but an actress (who let's be honest isn't that great) with ego issues has kinda screwed it up.