She can promise. And spend the time popping those bubbles? No thank you.
"She went through that bubble universe just fine." Clara walked up to the TARDIS and gave her a reassuring pat. Even if she was a mean old cow.
Her eyebrows raised as if to say 'What? It's a valid question!' That movie was completely based on the idea of having the Tree with all the different realms. That was the one he was talking about!
"We're at the roots." She repeated, then looked up at him. "Which means all our dimensions are like leaves on this tree's branches. We've blown down to the bottom."