As much as I like the innovative nature of solar and electric ion propulsion, both have by far more limitations (at current) than nuclear thermal propulsion and I hope governments finally start pumping serious money into nuclear technology again (and not just limited to space). We entertained the idea of nuclear thermal rockets and even experimented with it in the 60s already; they were proven to work as expected back then already but then got shafted due to change in policies. With advances in technology in the last 50 years this should be the right time and the next logical step in spaceflight if we want to make manned expeditions to other planets a feasible option in the near future. A few times better efficiency, significantly shorter transit time, more flexible launch windows - imagine being able to get to Mars in 3-4 months instead of 9 months? And maybe we can move from fission to fusion and derivative technologies in a few decades after that (hopefully even earlier); that would start a new age of opportunities in space exploration.
Back to more realistic things, 2020 is promising to be very exciting in terms of Mars exploration. NASA, ESA/Roscosmos and China are launching their rovers during the launch window next summer. Given that the launches are successful, we can expect the landing in early 2021 (February - March). However the European one seems to be racing against time and could be delayed until 2022.