Could he die and if so how will the series continue on without him?

Who would be the main character?

No that wouldn't make sense since he's the main character and if he did the series probably would contiue. As for who the main character would be I don't know.

I think once we start seeing someone else getting equal spotlight to Rick, i.e, Kirkman trying to make someone else a main character, then we can start worrying about Rick. Heck, he could die and it'll be just Andrea and Carl.

He could die and Carl could take over as the main character. By now in the comics there are plenty of interesting characters that could take over Ricks place. I don't really care if Rick dies, he's one of my favorite characters, but Robert Kirkman knows what he's doing. I've read all 120 issues and will continue to read it. The series hasn't been disappointed yet.

I think Carl would take over then Andrea being my second choice. They are the only other 2 characters who were from the original survivors in vol 1 who are still alive.

Absolutely he could die, and very well may. That's what sets the series apart from other titles. No one is safe, nothing is sacred.