Once a budget is allotted the money is there. Things do still get cut due to overspending and unanticipated costs as well. Very, very rarely do budgets get pushed up (RSRs at DCA got pushed way up due to John Lasseter, which made it the priciest theme park attraction ever built anywhere ... oh, he also had money added to the Nemo Subs redo at DL as well. On a park basis, TDS took funds that some -- talk to Eddie Sotto -- had earmarked for a new Tomorrowland at TDL and reallocated them.
But the economy, which should be in free fall (someone will have to explain what talking heads mean as a 'Post Wages' economy because I think it means that if you can't find a job or career that you just live off your wits like a zombie apocalypse or go on a shooting spree ... not really sure!) already since jobs are NEVER replaced in our alleged 'recoveries', won't impact this project. Once the money is allocated, it's a done deal (I keep saying that here so people don't say I always bear bad news!)
Indeed, I've been told that if the BoD waited just another 4-6 months to approve the DCA Extreme Makeover that it would NEVER have been approved based on our economy tanking and taking the rest of the world along for the E-Ticket ride!
Oh, and since you brought up the Monsters Coaster, I have heard nothing to indicate it being likely for the park. Part of me thinks it will be one of those attractions that are talked about for decades (see: WRE) that never happened.