Will I have my breast volume back after explantation?

What your breasts will look like after explantation  depends on several factors such as: the quality of skin elasticity (the better the elasticity the better the skin will bounce back),  the size of the implants used (the larger the implant the more trouble you may have with redundant skin), and the amount of breast tissue present at this time (which may have changed since the time of your breast augmentation). 
Life experience since your breast augmentation procedure, such as pregnancy or weight gain weight loss, will  potentially influence the factors discussed above. If you take these factors into consideration and apply them  to your specific circumstances you may get a good idea of what to expect after the implants are removed.
 
Occasionally, I see patients who just want the implants removed because they don't want the implants "to be a part of them" anymore.  Make sure you think about this and that this is the right thing for you.  It's difficult to say if you need a lift after removal -- no one will know exactly what your breasts will look like after the implants are removed until it is done.  Talk to a well-trained and experienced board-certified plastic surgeon and get good advice.
Best wishes.

Viola,
I will assume that you have already had your implants removed.  It is unlikely that your breasts will return to their pre surgery state.  Your breast tissue has been compressed and the breast skin has been stretched out, so you will likely remain wider and flatter. 

Unfortunately it is hard to predict how breasts will look after removal of implants. Your experience is fairly common after removal.