SQL Server 2014 CTP 2014 expiration date
The service will not startup after the date mentioned.  Prior to that date, you will need to obtain the SQL Server 2014 RTM to continue using the product past the end of March.

This is a bit of conjecture on my behalf, but since Microsoft almost never releases a third community technology preview (CTP) edition of any product, they are highly likely to make the RTM version available to MSDN subscribers within the next week or two, and then to everyone shortly thereafter and certainly before the end of March.

Just announced; Microsoft has RTM'd SQL Server 2014 for GA on April 1st.  No joke.