• With the mega pharma mergers that keep cropping up and are likely to continue into the future, what is the impact felt by CROs?

As a CRO/CMO I would say that this has been a significant factor in the past but less of an issue now. This is clearly summarized in the following article and its Table 1, reproduced below:
https://www.sciencedirect.com/science/article/pii/S1359644615003797

The article also makes clear that a more recent trend is one of increasing specialization and divestment rather than all-encompassing acquisition and merger.

That is not to say that concerns don’t exist for CRO’s and CMO’s from reliance by many large pharma companies on new biotechs for in-licensed discovery which can result in lost continuity of supply as biotech clients are subsumed into big pharma who are then better able to provide supply without necessarily relying on the biotech’s contractors.

A greater worry perhaps is funding and breadth of research for early phase R&D since big pharma tend to be risk averse and more interested in late clinical phase prospects such that early phase research (feeding the global industry pipeline) is jeopardized or at least narrowed in scope by inadequacy of early phase funding.

Please note that these are personal comments not necessarily representative of the views of my employer.