Since I got so many differing answers on this.. I called SRT. Spoke to Duane (whom I've chatted with multiple times online asking about my order

). Great news. Duane at SRT confirmed that for SRT Hellcat owners, if your Hellcat is in Dodge SRT service during the warranty timeframe for a warranty-covered repair, SRT will arrange for either a loaner vehicle or pay for a rental car, for up to 5 days. So this is great news.
I then asked "what if it takes longer than 5 days to repair and the car is undrivable? (i.e. engine failure, etc)." He said that would be on a case by case basis but it's very likely the loaner or rental would be covered till you got your car back fixed.
And what about oil changes / non-warranty service? "Nope, we don't do loaners for that."
OK... so not quite as good as luxury brand service, but still a lot better than worst-case-scenario..