Depends on how you define being a 3rd party publisher. If you mean basically being like MS where all their games will be available in as many places as possible, then I think the answer is no. Or not until after PS6.
PS5s are selling. Dualsense controllers are selling. The PS Portal is selling well (with Sony doing a Cloud handheld before even MS could). There's talk of a PS handheld (similar to the Switch).
Outside of the isolated case of MLB, Sony isn't brining their content to Xbox. Outside of MLB and the Lego Horizon game, it remains to be seen what Sony would bring to the Switch and Switch 2. Opening up to PC may be profitable enough for them, especially if a few more live service games take off.
For Sony, I am pretty sure that getting users into their eco-system is a core aspect to making money, and even with their PC expansion I don't think that is any less true.