Let's look at this from a poetical standpoint:
Kakashi knowingly and willingly sacrificing his life to save someone of his village is a very poetic, awesome way to die. It goes along with the whole "I will protect everyone no matter what" theme.
Now, let's look at this from a legistical, factual standpoint:
Kakashi's battle with Pein has been... 3 or 4 chapters. The 3rd's battle with Oro was much longer. Jiraiya's battle with Pein was much longer as well. Now, I understand Jiraiya and the 3rd are both much more powerful than Kakashi, but Kakashi's a main character. Possibly more of a main character than Jiraiya and the 3rd. It just doesn't make sense for him to die so quickly and easily.
Let's combine the two stands:
Kakashi should eventually die in this way. However, it should be after a much longer, hard-fought battle. He should die protecting someone, but definitely not this quickly, and definitely not Choji.
I could see Kakashi dying here, but that would be a major, major, major mistake from all standpoints, and I would be very disappointed in Kishi.