Connecting 4 servos, 2 motors, hc-05, sr-04 and L293D to Arduino
1) Is 6V supply enough for 4 servos and 2 dc to work?


If the motors are 6V motors then 6V is not only enough, it is what you need. What you should be asking is "Can my power source provide enough current.


  2) Is the connection between L293D and 2 DC motors correct?


Not quite. You have only got half your grounds connected up. Also 3,4EN should be connected to Vcc1 not Vcc2.

1A/2A and 3A/4A are the direction/break pins (one high and one low for a direction, both low for break). The EN pins can be (if you wish) used to control the speed with PWM (if you have any spare) - if not then they should be tied to the logic supply voltage, Vcc1, not the power supply voltage, Vcc2, since that can be up to 36V and is way too high for logic inputs like EN.