Welcome to Cayenne @marekorzeszko!
I'm not exactly sure where the agent is headed right now. Maybe @bestes can answer better? It will be released as open source very soon (if not already) but I'm not sure exactly what that means for us. Will we be able to add extensions and new sensors/actuators? If so the community can work at whatever pace we want to add sensors.
Regardless of the agent itself, there are currently 2 ways to get data from a DHT11 sensor on to your dashboard, Arduino and the MQTT API. I cover both ways here (MQTT through the Raspberry Pi):