Has pure Buddhism now been lost from the present sociological environment (lost from today's world, lost from present society), until the Maitreya Buddha will be born?
Pure Dharma can be defined as clear, unmistaken explanation of the path all the way to complete awakening, endowed with Buddha's blessings.
"Buddha's blessings" here mean that a teacher doesn't only say words and explain theories, he also does it with proper atmosphere.
For example, some lecturers might explain "correct words" but with disrespectful attitude or with restless mind, and so these "correct words" are not well perceived by listeners, so they will not practise them.
Unmistaken explanation means, in particular, that words correspond well to the situation - it's not like explaining a teaching poorly suitable for the present case.
Thus a good teacher should have clear understanding of what he teaches and how that relates to our situations;
he should have clear mind - with proper attitude and "atmosphere";
he should speak what he knows and refrain from speaking what he doesn't truly know.
Expounded with clear mind, explanations are clear.
With correct "blessings", they are accepted by people and inspire them to practise.
There are such teachers nowadays: they practice thoroughly, they awaken, and they teach clearly.
Thus pure Dharma exists now, it is not lost.
It is predicted that Buddhism will vanish in another 2500- years, regardless of the present situation. Maithree Buddha will take much longer to appear in the world. Roughly half of an Antah-Kalpa and some.