Will there be a crater deformity if all breast tissue and fat tissue are removed?

It is very likely that if you have all of the breast subcutaneous and breast tissue removed that you will be left with a contour deformity.  As you are thinking of achieving your goals make sure that you working with a board certified plastic surgeon,  who will know that one of our goals is not to "overdo" the resection. Best wishes for an outcome that you will be very palesed with.

Surgical reduction of gynecomastia seems as though it would be relatively simple and straightforward – just ‘remove the lump’ and the chest will look normal. But it is actually a deceptively challenging procedure that requires detailed preoperative evaluation and planning, a rational and stepwise surgical approach, and careful attention to detail in the operating room with assessment of chest contour several times over the course of the surgery with the patient in upright sitting position (as stepwise contour correction is performed).
There is always much more to consider than the overgrown breast tissue mass when treating primary (not previously operated) gynecomastia patients. One must pay close attention to the surrounding subcutaneous fat excess which is present in the majority of patients, as this must be treated – and treated in a manner that ‘feathers’ the breast tissue and fatty tissue removal peripherally so that there is no obvious demarcation between the area where tissue has been removed and the area where no tissue has been removed. Also, the chest skin must be carefully assessed in order to determine whether and to what degree it contributes to the preoperative appearance of breast tissue excess.
In my practice we see a fairly significant number of patients who have had gynecomastia surgery elsewhere and who find themselves with post-surgical chest contour problems. During preoperative assessment of these patients, it is important to determine how each of the following anatomic concerns contributes to the visible contour deformity:
Condition of the overlying skin, with particular attention to whether or not skin laxity and/or skin tethering is part of the problem
Degree to which breast tissue has been over-resected, and whether or not there are adjacent areas where breast tissue has been under-resected
Volume of fatty tissue excess (or areas of fatty tissue under-removal) peripheral to the area where breast tissue has been removed
Extent of post-surgical scarring which can tether skin and subcutaneous tissues, altering chest area appearance in neutral position and/or with arms raised
The good news is that the vast majority of these post-surgical contour problems can be corrected, and many of them can be corrected completely so that patients have a normal post-correction chest contour, with surgical scars that are inconspicuous or even completely invisible to the casual observer.
The last issue that is assessed and treated is laxity in the overlying chest skin, which can permit some soft tissue contour problems to persist, at least to some degree, if it is not addressed. The dermis of areolar skin is much thinner than the dermis of the surrounding chest skin, which means that it has an inherently lesser ability to contract and smooth out following the correction of problems involving the underlying fat, breast tissue and scar tissue.
Every effort is made to limit the amount of skin excision that is performed, as surgical scars become ever more obvious as the amount of skin excision increases.
Make sure your board-certified surgeon can clearly explain to you their stepwise plan for chest area contour correction, ideally while drawing on your chest with dry erase markers to outline each step of the plan, and that they can show you side-by-side ‘before and after’ photographs of gynecomastia correction cases that show clear improvements in chest contour with scars that are faint or invisible. 

The simple answer is that "yes", if you remove all of the fat and tissue, you will be left with a crater deformity. Which is why we don't remove all of the tissue. There needs to be some tissue to support the nipple. Assuming that you are seeing a board certified plastic surgeon with a lot of experience with gynecomastia, this should not be a concern. Best of luck.