Sorry to be that person, but I absolutely do not care one way or another for titans/mechas to be added to this game. Like, at all.
This wouldn't be the game I signed up for anymore if they did, tbh.
I think they will do it as a LTM to start to try it out. It's the same kind of addition that solos, duos, shotguns/snipers and the Halloween event are for them... a way to test new things to get data for future alterations.
One thing that's very evident in all the Respawn games so far is that these people really know how to make videogames of this type. They are pushing boundaries in all sorts of subtle and not-so-subtle ways. Think about simple things like how doors work in Apex. Get behind it and it can't be opened without kicking it in/blasting it open. This makes the simple door a tactical consideration! Who thinks of that stuff?!
With that in mind, I'm sure they are conjuring some really interesting things they can do with Titans and possibly with pilot abilities from Titanfall.
I have always thought that one reason Titanfall only marginally caught on was because they provided
too much change too fast. Many people could not wrap their heads around the supreme freedom of movement combined with a vastly diverse and unique set of weapons and abilities all at once. What Apex did was actually remove things from that formula to allow them to teach you how to play Titanfall-type games in a fast paced, short term battle royale setting. Now they can add things like wall running or Titans to the mix and those that didn't get it the first time around will be like, "Holy f--k! Where has this sort of mobility and RAW POWER been all my life?!"
I might be wrong that their goal is to work back to that, but I think the way they've handled the game so far points to that being the ultimate goal over time. Think also about how much Fortnite has changed its mobility options over time... it's gonna happen.