If you are planning to buy one of these cars the Ford Classic is a good option. The Dzire is still a great choice based purely on its value for money packaging which Ford hasn't been able to pierce. The Etios on the other hand makes sense if you want to buy a Toyota for brand value; otherwise it is a little more expensive than the Dzire.
Ford Classic is a good car and even if the car is discontinued Ford will keep its parts for at least the next decade. In comparison to Etios it may be an old car but it can easily match Etios performance and comfort. Though, if you are planning to buy any one of these we will suggest you to wait until Ford launches its next car, the Figo Aspire. Know more about Ford Aspire: http://www.cardekho.com/carmodels/Ford/Ford_Figo_Aspire
The has been no such announcements from Ford motors on this. So the model is not being phased out in near future. But, yes eventually the model would certainly be phased out, but when is that going to happen is not certain.
No matter a car discontinue or not, the manufacturer makes the parts available for a good 8-10 years after it is being discontinued and as manufacturer uses the same engine in multiple models, there is a higher probability that you can get engine parts easily.