Fellas, is it gay to sacrifice yourself to save Shinji?
This is all just a theory, but... What if Tezuka isn't predicting the future? What if he's actually able to semi-remember the events of previous rider battles? For reference - and obvious spoiler warning here - Shiro Kanzaki has been repeating the rider battle multiple times, trying to get it 'right'; he wants the strongest soul to survive, so he can then defeat them as Odin and use their soul to save Yui. But every previous time has been unsuccessful, mostly because of the one uncontrolled factor - Shinji Kido. Shinji wasn't meant to be a part of the Rider Battle, so the fact that he accidentally stumbles into the battle every time is a massive pain for Shiro. Shiro is the only one able to recall previous rider battles, but what if Tezuka was also able to, just on a far lesser scale?
Perhaps because he, too, wasn't originally the one chosen for the rider battle, or just because he has an especially strong intuition. For whatever reason, my theory is that Tezuka can remember just enough of previous battle iterations to know what's going to happen based on past events. For example, if Verde always dies early on, then he'll be able to intuit his death before it happens in the next Rider Battle.
This theory has some pitfalls. Tezuka prophecises that Shinji will die, but ends up subverting the prophecy by dying in Shinji's place. My theory suggests that this means in a previous rider battle, Shinji died early on, or Tezuka has died in Shinji's place more than once in this same way. I don't think this is entirely unlikely, it's just kind of inelegant. There's also the matter that Tezuka can foretell things unrelated to the Rider Battle, and that sometimes we're shown mysterious things happening when he makes predictions.
Whether or not this theory holds weight, it's interesting how Ryuki plays with the concept of the battle iterations and how retaining memories of a past battle can give you an edge in the next one. For example, Asakura remembers the previous battles in Ryuki Rider Time, and so does Goro. Ren and Shinji eventually regain their memories, but it takes them until the end of the show to do so. It makes me wonder how similar that makes Asakura to someone like Nogami Ryotaro, who is a Singularity Point - someone unaffected by any changes that may happen to the past, no matter how drastic.