nah, I played that series when it was first released on PS1 and got Days Gone day 1, in order to even fucking get any connection, you need that Easter egg......to need something like that means clearly its not some direct thing.
You didn't need even 1 easter egg in Back 4 Blood, its 4 people fighting zombies, Left 4 Dead is 4 people fighting zombies.....
So even as someone that played that series, this connection is too fucking loose to really say some direct sequel type thing. They share the same universe, thats about it.... I don't see anything else gameplay wise, concept wise, literally in the design of the game to really say something like direct sequel and I've played majority of Syphon Filter series. As it stands, I do not believe being in the same universe is enough to argue direct sequel or spiritual successor.
Would be like the ending of Horizon Zero Dawn 3 : Fight For The North, you find the helmet of a Helghast in a cave and be like "direct sequel to Killzone SF everyone" lol I'm sure they might exist in the same universe mind you, I'm sure one comes before or after or some shit, but that type of thing is not enough to say something as odd as direct sequel or successor, it just means they are in the same world, not that they are the same genre, game and should be played back to back as some connection or some shit.
So i'm 99% those that MADE Days Gone fucking know that, so any rumor about Syphon Filter successor likely really is about some spy in some open world setting actually doing the concept and ideas based on Syphon Filter, not a open world zombie survival RPG bud. I'm pretty damn sure thats not what any of this means btw.
Varteras
likely, but its sounding more likely that we see that Splinter Cell remake before we see this tbh.