The Department of Defense and several independent studies have examined a variety of alternatives to the current submarine and found that none of the alternatives are acceptable.
Diesel submarines wrong ships for the United States.
They do not have the mobility, covertness, endurance or firepower to meet U.S. military requirements for submarines. Building or retaining older classes of submarines does not meet U.S. needs or save money. Existing classes of SSNs, including 688Is, have limited margin for future improvements. Needed improvements in stealth, payload, and sensors require a new submarine design. Older does not mean cheaper.