User blog comment:AldenHeathcliffe/Chapter 551: The Burnt Offerings/@comment-10630156-20131003080937/@comment-6657474-20131007020845

HollowKing17, retreat is certainly a viable option in this situation, but I doubt the Human World or Hueco Mundo would be realistic options. For one thing, retreating to Hueco Mundo would require opening a garganta, and it's unknown how many others besides Mayuri have the ability to do so. Also, even though Urahara and co. are there, we don't know if they've managed to eliminate the Quincy presence there, also since the Wandenreich have invaded Hueco Mundo once already, the Gotei 13 wouldn't have time to regroup before the Stern Ritter followed them there. As for the human world, although the difference in Reishi concentration would give the captains an edge, they would be unlikely to want to cause more damage on top of what the Wandenreich's mass-hollow extermination has already caused. If you ask me, the only viable location would be the Royal Dimension, since that seems to be the only realm which the Wandenreich hasn't been able to infiltrate. Its safe to assume that those in the Royal Dimension are already aware of what's going on in the Soul Society. As for Ichigo, although I'm sure he'd be in a rush to return to the Soul Society the moment he found out about the attack, he can only do so if one of the Royal Guard allows it.