Not once you're a govt contractor. Colt hasn't made all the M-16s over the years.
If issues come up the govt comes down on you. If production needs to be increased. The Govt specifies an alternate manufacturer once you're making gear for them. FN & other manufacturers have made M-16/M4s for the govt.
The same will happen with the new weapons if the govt requires a higher production rate than what the primary can handle.