$60K is pretty steep for most people. If you can't afford it now, I would just keep saving for a couple years and then in 2017 see if you can buy a used low mileage garage kept 2015 Hellcat for $45-50K. Anyone who buys one of these cars is going to take awesome care of it and it will depreciate like any other car over a couple years. I don't think they'll depreciate as fast or as much as a more common Challenger model but all of these types of cars depreciate. You can find 2007-2008 GT500's in the $30K range with low miles nowadays and they sold for $50K when new.
The other reality is this. You could keep your current R/T, and assuming it's paid for or close to paid for, you could take an additional $20K or so and buy a car that's as fast or faster than a Hellcat and use that for racing/weekend fun and still keep your Challenger too (i.e. older car someone already did all the engine/drivetrain work to. Lots of nice older fast cars out there for $20K or so). Then you have two cool cars for probably less than the cost of one new Hellcat.
Obviously buying a brand new Hellcat would be the coolest, but just trying to point out some other alternatives.
Otherwise if you're set on getting a new Hellcat, I'd set up a spreadsheet and figure out how much you need to save for the timeframe needed and start setting that amount aside.