Folks lets not jump the gun while speculation is good, nothing has been said about Greg getting killed off, as to contracts alot of stars don't want the info released either until a certain time, or ever, and the other possiblity is that they are still in negotations, which can go in while they are shooting episodes.
Examples is back when George and Jorja were fired for a short time before being rehired back (for more on that do a search for those threads), at that time the negotations were also going on for William, Marg, Gary, Eric, Paul as well. All that was released on that at the time was that GD, ES, & PG all agreed to take a tiny raise and more air time, where as JF and GE fineally got rehired back but did not recieve the same offer but rather came back as they were before. WP and MH's Contracts were settled as well. -- But while the negotations were going on, the actors signed a paper agreeing to work until all parties finialized their negotations.
As to my comment about not jumping the gun, a season or so back there was a rumor that they were going to kill greg off in that season, and it turned out to be just that a rumor. Like I said while speculation is fine, lets remember that getting to far ahead is only cause confusion, ect.
Besides there are other ways if a contract is not re-signed that a character could leave and that would be by choice, Greg could get an offer to work at a private lab, he could get an offer out of state, ect. The thing is we just don't know and getting upset about it, while its of opinions, could be getting upset for nothing in the long run.
I personally and sticking to the spoilers and eps, each at a time, and not getting to far ahead. As to the "Casting Sides" I am not real sure how realiable they are considering they are for the purpose of casting and may not actually reflect the actual out come persae, why would they release all that information to someone testing for spot only to have them in turn not get the part, get ticked off and post it online. That just wouldn't make sense to me, My guess is they reveal only a little and more then likely its all un-edited, so then anything in that could be changed, like spoilers they are also un-edited and subject to change and
should be treated as what might happen and not what will happen.
Again thats just my opinion.