Here's a link to a recent 'Focus Note' by CGAP, summarizing the results of a 'scenario-building exercise to help anticipate and prepare for the (...) forces that will shape the future of microfinance'.
A quote:
" ... it is essential to temper expectations about the extent to which microfinance can eliminate poverty or reach the very bottom—destitute households—sustainably. A realistic evidence-based story must be provided. The search for better measures of impact remains an important
strategy to prepare for the critiques that will inevitably come and capitalize on the real potential of microfinance."