Right now, the word going around for UFC 100, is that there are going to be all titles on the line, and some huge mega fights.

We can now confirm to you,that this is not the case, but the UFC still does planning on putting on some huge fights for the show in a interview with Dana White:

"You know, i hear alot of shit, rumors about UFC 100, and to be honest, all titles won't be on the line for the event. It won't even be possible. Right now, there are some fights that could happen, we aren't even fucking looking at that. We have shit that we need to focus on then, then we can talk about that shit"

Looks like he is not planning on putting on all titles on the line, but some huge mega fights are surely to be planned.