Firstly, it is not an abstract way of saying that. It is very concrete! "not yet" is a standard phrase in English. It simply states: It's going to happen, but not now and not for a while. not for months yet = not now and not for a few months, but I'm definitely going on holiday.

lvirtuozlrus, In your sentence "yet" indicates "how long something will last" or "from now until the time mentioned has passed". -Not for months yet = still for two months -He will be working for at least two hours yet. -It will be some time yet before I am ready to conquer the world. Without mention of the amount of time "yet" can refer to the indefinite future. -We might yet see her. -The team could yet suprise us all. -Godzilla may yet destroy the entire city. -We will yet see the predictions of the ancient Maya's come true.

In my opinion, we use 'yet' to emphasise the time - as if to say it will be a long time. If we wanted to just say the statement, we would say 'not for months.' But when we use 'yet' in this way, it means we feel the time still left is quite long.