Yes, the ecobee4 will be able to connect with the same room sensors used with ecobee3.
If you need to re-pair your room sensors with your ecobee4, just follow these steps while standing in front of the thermostat:
1. Remove the circular backing from the back of the sensor.
2. Remove the battery from the battery slot.
3. Gently lift the prongs in the middle of the battery slot with your index fingernail.
4. Place the battery back into the battery slot with the positive side facing down.
5. Remove the battery and place the battery back in with the positive side facing up.
6. Place the backing back onto the battery slot.
A message should appear on the thermostat screen asking you to pair the remote sensor with the thermostat. Follow prompts from thermostat.