Probably earlier in April than we wanted.
The official cutoff time for those Wonder Trades in Pokemon Sun has been announced.
Nintendo has updated the support article regarding the shutdown of online gameplay on the 3DS and Wii U. The update indicates that the service will end on April 8 (Monday), at 7 p.m. EDT.
Originally announced on October 3/4, the service will affect both direct online services as well as 3DS's SpotPass service, which can remove content from games such as Fire Emblem Awakening. The services for Pokemon Bank and Poke Transporter - which can be uploaded to the current Pokemon Home service - will remain online beyond that, but are subject to their own end date.