There are lots of changes in terms of this issue, to the point that I don't remember them all... thankfully the bits that are changing are listed (and described) on the official website:
https://www.formula1.com/en/latest/a...MQImMiIgw.html

A condensed version of the list of things that are changing for 2019:
  • Front wing is simplified - which will encourage designers to direct air under the car, which is affected less by following another car.
  • Rear wing gets wider and deeper (with no slots on the side) - which should direct the disturbed air far enough upwards that it wont affect somebody behind.
  • DRS (the bit on the rear wing that opens to help overtaking) gets bigger - so should be 25-30% more powerful.
  • No brake duct winglets, and no blown axles - both of which direct air outwards (which affects the car behind).
  • Barge boards (the 'wings' parallel to the car beside the driver) are moved - to make them less sensitive to following another car.

This is just a small part of the changes that are intended for 2021, but as the teams all agreed the bits above happen next year - and seeing the results of these changes will enable the officials to come up with an even better design for 2021 than they would have (and they don't need the teams to agree to that design, as the governing body can force it then).

Just the things for 2019 should make a big difference to this issue (and alter which cars are fastest), so it could be a very good season.