If there is a patent that covers what preact or vue do, then yes. A patent on "react" would not use the term react (it might not even mention JavaScript or web browsers), and it applies to any implementation of a particular concept. So if some aspect of React's DOM handling is patented then anything that implemented DOM handling (patents are a bit more complicated but bear with me) would be a patent violation and any user of the code could be sued. You can also be sued even if you are just a user of a project that uses preact.