That's not a serious option.
However, they already have a trade deal. They could extend it, participate in joint R&D programs, etc...
The lesson of recent events (Covid pandemic, Ukraine invasion, Trump's expected policies) for any country or Union, is that it's dangerous to depend too much on one country. One can expect the EU, Canada, China, etc... to reduce their dependence on the U.S. Same for other countries to reduce their dependence on China.
The future dominant strategy will likely be to manage to get a more balanced and more diversified portfolio of economic partners.