The new issue of Corocoro magazine has revealed new details about the upcoming Pokemon generation. These new details show that Eevee will be receiving a new evolution. The Pokemon will be named Ninfia in Japan, which is similar in name to other Eevee’s in Japan (Leafeon is Leafia and Glaceon is Glacia in Japan). This means that Ninfia’s English name will likely end in –eon like the other Eevee’s (the name could possibly be Nineon or Ninfeon). The type and method of evolution for Ninfia are also currently unknown.
This announcement also brings up some other indirect announcements. For starters, in the past when Eevee gained new evolutions she gained 2 new ones at a time. So it is likely that there will be a second new Eevee evolution. Also, this announcement means that other old Pokemon may be receiving new evolutions. In generation 5, no new Pokemon were evolutions of older Pokemon (even though some, like Alomomola, looked like they should have been). In generation 4, several older Pokemon gained new evolutions, which were welcome additions for some of them (many were rarely used before due to their poor stats). Hopefully, some of the less used older Pokemon will get evolutions in this upcoming generation.
The two websites below have additional details about the announcement and have translations for the major details in the scans from Corocoro.