The word 'Hosanna' refers to an entreaty for deliverance or an expression of celebration for the coming of salvation. As the people celebrate the arrival of the Messiah, Jesus, however, foretells that Jerusalem will be besieged from all sides and the people will be scattered or wiped out. It is because the people do not realize who the Messiah is and what He has been sent to accomplish. 
A time of peace and prosperity under the rule of God's anointed King had to be postponed due to the shocking rejection of their Messiah and King, His illegal trials, and cruel crucifixion on a Roman cross. Although the kingdom of God has been on hold for almost two thousand years, God continues to fulfill His redemptive purposes through the Christian Church.
A day is approaching when Israel as a nation will cry out to the Lord for forgiveness and salvation. When Christ returns, He will establish His kingdom and restore the throne of David on earth with all His holy ones, the Christian Church. When that time arrives, the entire nation of Israel will recognize the Messiah and once again cry out for salvation.

Dear Heavenly Father, it is an amazing grace of Yours that Your only Son was able to come to earth and take away our sins as the Lamb of God. It is a blessing that Your plan of redemption allows everyone, Jew or Gentile, to be saved. Thank You for all of Your plans and purposes for saving mankind and restoring the world. May I live my life in a manner that honors Your name at all times. 
In Jesus's name I pray. Amen.