Of course, you can always use conventional jet engines to get to Mach 2.5 where conventional scramjets cut in and take you to Mach 5-7 where new design scramjets take over and boost you to Mach 10-12, then you go to rocketry.

It adds an extra stage of complexity but allows you to incrementally develop the technology by using a conventional rocket for now in place of the yet-to-be developed new technology scramjet.

I can't see a system as complex as this being of value for small payloads. It would have to be a medium to heavy launch system so that there was enough oxidiser saving to trade-off for the extra stage weight and risk of another intermediate stage and another set of scramjets.

(or you use a rocket as first stage to go direct to the performance envelope of the new technology scramjet stage, and while you're waiting for that to be developed, you use a conventional rocketry second stage. - Hey, isn't this an EELV, or the long awaited new heavy booster? Maybe one of the CON-tractors could sell NASA a new technology scramjet that nobody ever really intends to work, and use the development money to fund a new HLV????)