http://www.inis.gov.ie/en/INIS/Pages/in ... aty-rights
If your application is still being processed - At this stage, no specific action is required from you if your application is being processed.
If you are the holder of a valid Stamp 4 EUFam card - As a person who is currently entitled to avail of the European Communities (Free Movement of Persons) Regulations 2015, you should have no concerns regarding your continued residence in Ireland after the 29 March 2019. In a no-deal scenario you will no longer be subject to the provisions of the Free Movement Directive and the exercise of EU Treaty rights and entitlements. However, arrangements are being put in place for non-EU/EEA family members of UK citizens who have been exercising Free Movement rights here up to 29 March 2019 to facilitate their transfer under domestic immigration arrangements to provide for their continued residence in the State. Insofar as possible, the objective is to retain similar rights to those that you would have enjoyed as a family member of an EU national including access to the labour market.