It depends. One factor is the life-cycle of your products. For products with life-cycles of 20+ years, you should start preparing now. For shorter life-cycles, you may be able to wait until your next development cycle, and then make Y2038 compliance a requirement.
Another factor is your business infrastructure. Most companies have business infrastructure tools and data which may have been developed in-house or purchased/leased from third-parties. These systems may be quite complex and may have taken years to deploy. The original developers may or may not be available to assess or mitigate Y2038 issues. Therefore, the assessment/mitigation effort may be large and may include migration of data. Companies that wait too long to prepare will be competing for limited technical resources as 2038 approaches and may find it difficult to secure the resources in time at a reasonable cost, thereby putting the business itself at risk.
The main point is that the Y2038 effort should not be underestimated. It is far better to proactively assess and mitigate as early as possible.