The short answer is: no, it is not planned to support tf1 in ROS 2.
The slightly longer answer: tf2 is the successor of tf and available for a long time. The use of tf is deprecated and it should be fairly easy to upgrade any code. It might even be the case that tf 1 won’t be released in a future ROS 1 release. Therefore spending any effort on support tf 1 in ROS 2 is considered not worth it.