It means a long time in the future.

Indefinite time periods are always relative. In your example, "a while" is probably somewhere between a few days and a few months. But "a while" can mean anywhere from a few minutes to a much longer time period. For example, if you're talking about geology or evolution, "a while" could be millions of years.

The phrase "a while off" is an informal way of expressing that something is not going to happen soon or in the near future. In the context you provided, the speaker is suggesting that the arrangement can be made, but it won't happen for some time. It indicates a delay or a period of time that needs to pass before the mentioned event or arrangement takes place. In other words, there's a considerable amount of time to wait before it happens.