My first thought was it's just the current jobs plus arc/smn to show off the new stuff front and center. But it's certainly possible it's a scholar. After all, if SE were to make 2 new mage jobs by release, it would make sense time efficiency wise to take the arcanist/summoner and tweak it into a second class/job. In fact, it's almost the only way I can see them adding another class/job to the game by launch. As others have mentioned, the two new proposed class/jobs using grimoires/tomes would mirror how black/white mage worked with similar weapons so it wouldn't be that strange in my book (... no pun intended ^^"). Add to that how closely it resembles ffxi's scholar class and how the image in question only features jobs in front and you have a very persuasive argument.

I'm hesitant to think SE will announce a two job per class system on top of a scholar class. To me, it'd be strange for only the new class to get two jobs while everything else is stuck with one. If they did, they'd probably announce that they plan to release a second job per class after launch would be also be a huge bombshell.

But until I get some official word from the devs, it'll have to remain as arcanist for me. But here's hoping! The more classes/jobs the merrier.