By refueling the SpaceX BFR in orbit and assembling a few stages in high orbit, a large chemically powered space mission can get up around 9.0 kilometer per second delta-V.
We will not need to wait decades for super-advanced space propulsion to be developed for less than 60-day trips to Mars. Elon Musk and SpaceX should have the BFR flying within 5 years.
Short 45-60 day or even 30-day trip using large multi-stage chemical rockets launched from high orbits after refueling will make large fast missions easy. The shorter times mean far less radiation and health issues for astronauts and passengers. The far larger ships means water and other material for radiation shielding.
The Mars missions we have sent have been less than 1000 kilograms but putting a few BFR payloads together could send 1000-ton Mars missions.