I'm still running a Mugen 7R fleet (7R Eco, 7R Nitro & 7TR Eco) and can still easily find parts at any given moment, moving to a 8R generation won't get me to the Worlds but will get me $2K shorter. Buying into the newest is entirely up to each individual and not always will make you any faster, just stay comfortable with what works with you and exploit it, nothing else to it.