If she records them, she'll almost certainly release them. Otherwise, what's the point? It's not unprecedented --a number of other artists have rerecorded their old work, when they've been unable to regain the rights to the earlier recordings. Typically, it's older artists who are just looking for a way to gain a bit of money off their faded glory. Accordingly the new recordings don't often compete effectively with the originals. Given an influential artist who is still popular, however, this might be a different story. The closest analog I can think of is when the Artist Formerly Known as Prince, in the thick of a war with his record label, rerecorded his hit "1999" to take advantage of its millennial popularity.
This is just speculation, but it's also possible that Swift doesn't really want to follow through on this threat, but rather, is using it as a way to gain leverage in her fight to get her old recordings back. If Braun thinks that the new recordings will substantially reduce the value of his holdings, he might be more willing to cut a deal. That's also not unprecedented (see above cite).
Perhaps the most interesting question is what approach will she take with the rerecordings? Will she try to do a perfect duplicate of the original? Will it be a slight update? Or radical reimaginations or modernizations of the songs? Artists have taken all of the above approaches. Nevertheless, it can be difficult for even the original artist to recapture old magic.
https://www.synchtank.com/blog/for-the-re-record-heres-what-you-need-to-know-about-re-recording-restrictions/
https://www.vulture.com/2019/08/taylor-swift-will-rerecord-old-albums-to-spite-scooter-braun.html
https://www.washingtonpost.com/arts-entertainment/2019/08/22/can-taylor-swift-really-rerecord-her-entire-music-catalogue/