1
general::
Within view, not too far away, as in The analysts see a huge rise in the stock market on the horizon.
American Heritage Idioms
2
general::
Phrase(s): on the horizon
1. Lit. appearing at the boundary between the earth and the sky. • There is a storm on the horizon. 2. Fig. soon to happen. • Do you know what’s on the horizon? • There is some excitement on the horizon, but I can’t tell you about it.
McGrawhill's American Idioms And Phrasal Verbs