It's not really that they're scared to drop the characters, the Lightning trilogy was decided pretty early (not talking about the FF13 / FF Versus 13 / FF13 Agito trio, but it was at least already decided when they started FF13-2) so it's not weird for them to go through with the story they wanted to make. If anything, it's simply taking quite some time to finish, so it feels to us like we're spending three numbered games on it.
If I struggled to the end of my determination, to the end of my way of life with my followers, if the result is ruin, then this ruin is inevitable. Grieve. Shed tears. But you cannot regret.