According to the launch schedule at the moment I looked (which is of course only a snapshot in time) there is a Cygnus mission (NG-11) scheduled for Apr 17, 2019.
There is a SpaceX Dragon Cargo mission (CRS-17) scheduled for Apr 25, 2019.
Cygnus and Dragon generally remain on station for about a month at a time, as the astronauts unload the payload, and reload it with trash (Cygnus) or down payload (Dragon, or the new tiny capsule for Cygnus).
There is a possibility of HTV and Cygnus in the fall as well with tentative mission dates of Sept and Oct for the two vehicles.
The question of whether NASA expects an open port for each docking attempt still remains to answered, as discussed in Docking Port policy for manned flights.
Worth mentioning that there are two available CBM (Common Berthing Modules) ports on the US side. These are used by Dragon Cargo, Cygnus, and the JAXA HTV vehicles.
The manned vehicles will use the two PMA (Pressurized Mating Adapters) with the inserted IDA (International Docking Adapter) units. (One IDA-2 is on station, IDA-1 was lost on CRS-7's loss of mission, and IDA-3 is due later in 2019 on the CRS-18 mission (May 2019, at the moment)). These will be used by the Dragon Crew, Boeing Starliner, and possibly the Sierra Nevada Dream Chase if they ever build it.
The Russian side has 4 docking ports used by Progress, Soyuz, and previously the European ATV, and we have seen almost all possible combinations.