Both forms exist, and we use them to refer to a situation which you are waiting to happen. For example:
'He's sent off an application for the job, but he's yet to hear anything.'
This means he's expecting to hear something, but he hasn't heard anything yet.
or
'They've put a lot of effort into the advertising campaign, but they've yet to see any results.'
This means that that they haven't seen any results yet.
This form is simply an alternative way of phrasing a present perfect sentence ( haven't seen/ hasn't heard) by looking into the future rather than the past.
In some ways, the 'am to' part of this construction is similar to the rather formal future form 'be + to + infinitive' which we use to talk about a scheduled event. For example 'The President is to visit Paris next month'.
The 'looking forward' aspect of the construction suggests the idea of expectation. It's a nice expression because it encapsulates past, present and future time. It hasn't happened yet, but you are expecting it to happen at some point. That said, it is by no means an essential construction to use. Use it if you wish, but there's really no need to! Plenty of native speakers get through their lives without ever using this construction, I'm sure.