Okay before I get into the idea, let's get some general information in:
First: Shanks requested to meet with WB, WB thinking it was war, but in fact Shanks only wanted to talk. We all get bad feelings about things, but was it a bad feeling that made Shanks come out of nowhere, usually said Yonko's never meet face to face? Why would Shanks risk that solely base on a bad feeling. I don't believe that was the case for Shanks.
Second: Shanks had a past with Blackbeard, that fact doesn't change and Shanks said so himself during the conversation with WB, that he wasn't being careless.
"Do you know what this means" was what he said after that.
Third: Shanks insisted that WB stop Ace from going after BB, that he should keep his hands off BB, suggesting he leaves BB up to him to deal with. Why? Why would Shanks do this? BB did indeed leave a mark, why Shanks is not the type to hold grudges.
Fourthly: I believe Oda didn't want to give out more information on haki, so he made Shanks say stuff like,
"Keeps your hands off BB",
"Stop ACE from going after him" and so on. That was not until we met, a yonko's commander named Katakuri, who can see a little bit into the future, he sees exactly what will happen to the person he is focusing on 2 or 3 seconds from now. Which has brought in this idea that Shanks foresaw exactly what BB would do, and his plans leading up to WB's death, I believe Shanks saw most or probably all of it.
Thus the reason why he went on to speak to WB, to try to stop BB from rampaging. I also believe Shanks meaning behind those words form my hypothesies that he knew it was coming, he foresaw something that led him to want to meet WB. I believe when Luffy finally meets Shanks, we'll either confirm that or not. Also to include, it might've been the reason why Shanks intercepted Kaido, he probably foresaw WB death, and didn't want to say it bluntly, so he attempted to try to stop ACE through WB to save him even though they're enemies themselves.
So what do you think of my Hypothesis?