"Until later" is a way to describe something happening in the future. I can't explain it very well, but here are a bunch of example sentences that might help: "I won't do it until later" = I won't do it now, but I will do it later. "I didn't realize until later that I forgot my umbrella on the train" = I didn't realize before, but I realized later that I forgot my umbrella on the train. "The weather forecast says it won't rain until later tonight" = The weather forecast says it won't rain right now, but it will rain later tonight. "She didn't arrive until later that afternoon" = She didn't arrive then (in the early afternoon), but she arrived later in the afternoon. "You shouldn't tell him that until later" = You shoudn't tell him that right now, but you should tell him later.

Notice that until later is used in negative sentences.\: I can do that later. I can't do that until later. Logically. the sentences are the same, but the second emphasizes "I can't do it now" (but I can do it later).

yeah, he'll be sure later