impact of migrantion crisis on european employment rate

The Europe’s labor force is aging and will soon begin to shrink. At the same time, the European governments have cumulated enormous debts that must be carried by future generations. This task can be challenging assuming that the next generations will be smaller. How can the European migration crisis influence/change these tendencies? What are the possible scenarios to be discussed here? Please explain possible migration impact on the natural unemployment rate, wage, the mismatch in the labor market, and economic growth in the short and long term.