Investors might want to wait to hear what Boeing has to say before they celebrate Monday's Wall Street Journal report that the company is starting to work on a new jet to eventually replace the 737 MAX. "Not so fast," wrote Jefferies analyst Sheila Kahyaoglu in a Tuesday report. "Although Boeing is likely interested in next-gen technology, it is likely more immediately focused on driving productivity and rate increases, improving the [defense business] outlook, coupled with the ongoing 777X development to help restore the balance sheet."