Unless the basis for scrapping the TN were somehow that the free trade agreement was unlawful/invalid or the TN itself were unlawful/invalid, I believe that it

Unless the basis for scrapping the TN were somehow that the free trade agreement was unlawful/invalid or the TN itself were unlawful/invalid, I believe that it likely would remain valid until expiration for work purposes but probably not for international travel purposes. What the other work visa options would be would depend on the person's qualifications and job; these would include the cap subject H-1B (but this is subject to an annual lottery), the cap exempt H-1B (available year-round but with a qualifying organization), the E-2 (requiring the creation of a company and an investment or employment with an existing E-2 qualified company), and the O-1 (requiring high standard of acheivement).