With the Chinook and Apache continuing production, for at least another decade, Boeing Philadelphia will continue to survive. However, Boeing has already lost all their engineering capability to develop new modern platforms. So it will be a slow death until these aircraft are replaced by newer models designed by either Sikorsky or Bell. If Boeing is part of a team in a replacement Chinook or Apache aircraft, it will only be in a manufacturing role.
It's arguable that Boeing never had engineering capability to develop new modern platforms. No helicopter of their own original design has eve rentered production. All their craft that entered service were designed by someone else and Boeing later acquired the company. In fact only for airframes of one of their own design ever even flew, and its rotor design benefited from Boeing's license production of the MBB Bo 105.