The OTV's are robotic only, but the follow-on would likely be crew-optional. They could develop something new, but the proposed specs for the upgrade almost perfectly match satellite manufacturer Sierra Nevada's NASA CCDev-2 commercial crew entry - the Dream Chaser. DC starts atmospheric test flights with captive carry flights under Virgin Galactic's White Knight 2 mothership in the next few weeks, culminating with drop-glides to robotic landings by the end of this summer. It's launcher agnostic, meaning that with a physical adapter it could fly on most any launcher capable of lifting it. Test flights will be on an Atlas V.
Dream Chaser specs -
lifting body (fuselage also produces lift, not just the winglets)
carbon composite pressure vessel and aeroshell, which allows special versions to be rapidly prototyped. Adaptable to servicing missions by adding a Shuttle-style cargo bay door, a bulkhead, small robotic arm and an airlock - already being discussed.
7.8 metric tons
2x hybrid rockets (a mix of liquid & solid that can be started, stopped, restarted & throttled.) These also serve as OMS and launch abort engines. The propellants are liquified nitrous oxide (laughing gas) and a synthetic rubber like fuel called HTBP
8,000 feet (could land at any commercial airport)
Dream Chaser artwork attached. Notice it has no nose wheel - it uses an old-school skid. This is much lighter, simpler and increases the payload mass. Steering is by applying differential pressure to each sides wheel brakes. You haul it off the flight line using a standard aircraft tractor.