Huge Grey's Anatomy casting news this morning. The six remaining original stars have all signed two-year contracts to continue with the ABC medical drama, keeping the core of the show intact.

This assumes there are two more seasons, of course. ABC has yet to formally order a ninth season of Grey’s Anatomy, though it seems like a foregone conclusion. The network reveals its 2012-13 schedule Tuesday.

Assuming Grey's is on it, Ellen Pompeo, Patrick Dempsey, Sandra Oh, Justin Chambers, James Pickens, Jr. and Chandra Wilson will all be back. The same goes for a potential 10th season in 2013-14.

Showrunner Shonda Rhimes has said it's been challenging to craft the season finale to the current eighth season while not knowing which members of the original cast would and would not return next fall.

“[It] was the most complex puzzle I’ve had to put together, ever,” she told TV Line this winter.

”We have all these moveable pieces of who’s coming back and who’s not, and finally I just decided to focus on what was going to be best creatively [and] make it work regardless of what is happening [off screen].”

The Grey's Anatomy season finale spoilers we've read so far suggest a very dark chapter to come tonight and next week, but it looks like Meredith, Derek, Alex, Cristina, Bailey and Richard all survive.

The original cast members were the only ones with expiring contracts at the end of Season 8; the rest of the ensemble remains signed through next year as well. Of course, there could be a major death.

In any case, it's terrific that ABC and the cast were able to get this done. Comment below!

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.