Generally no. What changes is the amount of scar tissue or thickness of the capsule around the implant .

The implants are always soft. After surgery due to swelling the implants feel firm. Once the swelling goes away the implants are soft. If your scar tissue gets hard then the implant will feel hard. This is an uncommon occurrence.

Saline implants can get softer over time. When saline implants are placed they are generally overfilled to prevent rippling of the implant. The implant has a semipermeable shell and tends to lose volume overtime