It's pretty clear they're not going to be making Tarkin. They had their chance with Rogue One and they didn't do it. I'm sure they're well aware he's one of their most requested figures, but for whatever the reason may be, they're not making him. Maybe they don't feel he's going to sell well or maybe they can't get the rights, but they're moving into ESB and ROTJ full steam ahead now.
I think the last hope for Tarkin is if they reveal him with Krennic and Cassian at SDCC, but given that Palpatine, his Royal Guards, ROTJ Luke and Hoth Leia are all going to be revealed there, I think the chances of Tarkin are dead.