Arenas will return?

Yes! Arenas will return as an LTM, mostly because people asked for it (And they finally did it!), so they're going to test engagement to see if it's worth bringing back as a mode. With a few tweaks, but regardless, I'm already super happy it's coming back!

More info regarding it, here: https://www.ea.com/games/apex-legends/apex-legends/news/prodigy-game-updates
Also some more info can be found here: https://www.reddit.com/r/apexlegends/comments/1kcauir/s25_prodigy_digital_preview_event_notes/ 

I would much rather arenas come back as a permanent mode. 

I didn't really start Apex with BR, my first season trying was when Fuse was new. 

I started when Valk and Arenas dropped. Arenas gave you a way to practice BR like conditions against real opponents in a focused way that wasn't over on your first death and didn't have to deal with 3rd, 4th, 5th parties. 

I really, REALLY miss the mode. If it came back permanent, I might never touch BR again. 

I agree! It honestly is what convinced most of me and my friends to finally pick up the game, and its the most fun we've had in ages!!