Confirming yes year round for OAK-EWR (SAN as well I assume)
Yes, confirming SAN-EWR is also permanent/year-round starting next April. (I believe the only reason it isn't currently year-round, from this summer when it began, is due to the fleet reconfiguration going on at WN. It was expected to go permanent as soon as the a/c was available; this was also said of the other 'seasonal' routes that WN began from SAN this summer: GEG and IND. They apparently decided to start with EWR -- coincidentally, a route flown from SAN for almost a year now by AS -- while GEG and IND have no competition (yet) from SAN. Makes sense to me.
WN rarely does 'seasonal' from SAN. The few routes that began as seasonal here, for whatever reason, became permanent pretty quickly. Currently, in addition to IND & GEG, the only other seasonal route is apparently MKE, unless it has been dropped and will not be back. Nobody seems to know what the status of SAN-MKE really is. It was announced as permanent when it re-started in August 2016, and was supposed to be running daily into this Nov -- that is, it will have run for ~15 straight months -- but now with an abrupt stop this Labor Day and no re-start set yet. Could be another fleet-related 'temporary' suspension, or...?