Now that Israel is declaring war on the Hamas, what should we expect to see in the upcoming days/weeks?

We should expect more attacks by Hamas and Islamic Jihad, as well as Hezbollah from Lebanon. This means that there is a serious possibility of a two front war for Israel as it strikes towards the Gaza Strip near the sea, and more north into Lebanon. Concerning the State of Israel, look for a massive air bombardment over the next few days until the conditions on the ground are satisfactory, according to Israeli intelligence, to send in massive ground forces. One can expect a full infantry onslaught with all that entails within the Gaza Strip and perhaps other areas as well. We could also seem so strikes against Iran, especially cyber in nature, but perhaps, much more kinetic than we can imagine given the emotions being felt by the Israeli security council.