Jacob pulled an Obi Wan-Kenobie by Andrew Stellatos

Jacob-It only ends once, anything that happens before that, is just progress.

MIB-Do you have any idea how badly I want to kill you?

Jacob-Yes.

MIB-One of these days, sooner or later, I'm gonna find a loophole, my friend.

Jacob-Well when you do, I'll be right here.

At first I took Jacob's line to mean he would accept the challenge. Upon watching season six though, it left me wondering if Jacob wasn't just accepting the challenge, but rather, telling him that he had already anticipated, and therefore, prepared for MIB's loophole. We've already seen him manipulating the Losties from the "afterlife", which tells us the game is still in play, or else why would he bother moving the peices (losties) about? Perhaps dying was always what he wanted to have happen?

As a side note, if he wanted to die, and Charles Widemore wanted Ben to get back to the island--cause if he didn't the wrong man would win--does this mean Charles was helping Jacob die? Which was what I think he wanted all along?

As I said, I think he pulled an Obi Wan-Kenobi

Obi Wan-Kenobi: You can't win, Darth. If you strike me down, I shall become more powerful than you could possibly imagine.