The European Commission published warning on 12APR that visa-free travel by US and Canadian citizens to Europe is at risk, due to the lack of a full reciprocal arrangement for EU citizens.
The core of the issue is this: Although US and Canadian passport holders can travel to Europe for stays of up to 90 days without requiring a visa, citizens of some EU countries are not eligible for the same privilege in return. Specifically, citizens of Bulgaria, Croatia, Cyprus, Poland and Romania require a visa for the US, and citizens of Bulgaria and Romania require one for Canada.
The deadline for US and Canada to include those citizens in their own visa-waiver programs expired yesterday, on 12APR2016. Consequently, the EU is obliged, under their own policy document, to take steps to remove the visa-free travel privilege for US and Canadian Citizens.
The United Kingdom and Ireland do not take part in the development of the common visa policy and would not be bound by a visa waiver suspension.
No change has yet occurred, and any decision to limit travel would have a lead time (most likely 90 days). For further background see the full EU press release.