Through QGIS 1.8 I have a layer whose data are updated every 3 seconds. The question is whether it is possible that QGIS Cloud can represent these dynamic changes?
It's an old question, but probably it's worth to answer it anyway. Publishing of real time data is possible if you fill in the data directly into the QGIS Cloud database you created during the data production workflow. You can connect to the data directly with every client which is able to connect PostgreSQL databases. For getting the connection info please open QGIS, login you QGIS Cloud account from the QGIS Cloud plugin. Open the database tab and hover the database of your choice. You will get the connection info as tooltip.