Would you put the same headlining act on the bill two years in a row? Never mind they didn't play this year, Mumford is still on all the posters and t-shirts and they were a large draw for tickets. Booking the same headliner two years in a row even if they didn't play isn't going to sell as many tickets in the second year. By then, the people wanting to see Mumford so badly will have spent that money to see one of their shows elsewhere.
They're at their peak right now, a year from now they won't be as big of a draw anyway.
I can see doing a make up date in two years (by then they'll be supporting a new album), but it won't happen in 2014.
Let's be clear that I'm not predicting it to happen, I'm saying that it isn't unreasonable to think it'd happen. I can't find it, but if you've ever seen the Mumford/Wiz Khalifa crowd shot from 2011 you'll know that Mumford was wildly popular in 2011, they're still wildly popular in 2013 and in all likelihood will have their next album out before Roo in 2014 (Babel came out in Setpember of 2012, so 18 months is more than enough time to release a new album).
I think you guys that are writing this off as "no chance" aren't really being fair. It'd end up being a show, probably before their Fall of 2014 tour, where they play a ton of new stuff and get a massive amount of buzz going. I think it'd make sense for both sides, to be honest.
I distinctly remember Flanzo and I arguing this time last year about whether there would be a WTT2 out in time for Bonnaroo 2013. Not trying to rub in the fact that I was right and flanzo's an idiot, just saying I'll believe it when it happens.
It was supposed to happen around Christmas (a friend was a PA on the WTT tour) but got pushed back due to children, schedules, etc. It will happen.