For a product still in development, you would need to ask the company whether a “life cycle assessment” has been done for that product. One might suppose a company's set of developed products is disjoint from its set of undeveloped products, but the statement “We carry out life cycle assessments on developed products” does not draw a sharp line between developed and undeveloped. With regard to current development, it is likely to mean “We carry out life cycle assessments as part of our product-development process.” But if “life cycle assessment” is a new activity at a company, it might instead mean, “We now carry out life cycle assessments as part of our product-development process, and we are doing life cycle assessments on our existing products as we find the time or receive grants to fund the work.”
The above assumes you are trying to interpret what some company has told you. If instead you are trying to describe the practice of a company, reasonable alternatives are to leave out the word developed if you mean the statement to apply to all products, or replace it with previously-developed if you mean to explicitly exclude products currently in development. Actually, you probably are best off leaving out developed in either case; most people do not regard items under development as products, ie, a product (of a manufacturing company) typically is a previously-developed item now available for sale.