I wouldn't get too excited if I were you. DBK (who is 99% on the mark with Ford leaks) has basically said Ford isn't going to be announcing anything soon that will out power the Hellcat.
Ford proved themselves already with the 13/14 '500s. They are stepping away from the big hp game and moving onto vehicles that handle and offer more driver enjoyment, as apparent with the popularity of the Boss 5.0's. I wouldnt expect them to venture into a 600+hp car for a few years, if they ever do so again. While I love the idea of the Hellcat, it is a few years late to the game. The 392's were always playing catch up and while this gives them a 50hp advantage, I feel this is still the case, especially with the lack of aftermarket due to Dodges nearly un-crackable ECU's and lack of support for tuners like SCT/Diablow. Youre gonna have a car thats ready to make an extra 50whp with a mere $500-1k spent but you gotta wait 2-3 years for the tuning side to catch up so you can actually install pulleys and get any gains from boltons.