Their relationship would likely deepen. The impending arrival of a baby would bring them closer together on an emotional level. They'd have to communicate more about their hopes and fears for their family. For instance, they might have long talks about what kind of values they want to instill in their child.
Another plot could involve them preparing for the arrival of the baby. They could be seen shopping for baby supplies in different alien markets. Quill would be clueless about most things, while Gamora has a more practical approach, leading to some comical situations.
Gamora's fate varies in different comic arcs. Sometimes she meets her end, but her story often has complex twists and turns. In some cases, her death is part of a larger narrative development or a sacrifice for a greater cause.