Battlefield 2042 hype caused a player spike on Battlefield 4, resulting in an intervention from EA.
Battlefield 2042 is on the road to success apparently as the hype for the game was extremely strong following the E3 announcement. So strong, in fact, that people started playing Battlefield 4 en masse.
The game wasn't deserted by any means but after the BF2042 announcement, enough players came back to BF4 that servers reached capacity and some had to wait in queues.
As a result, EA announced they would be expanding the server size temporarily. This change was applied only for US West as this region experienced longer queue times compared to others.
That said, EA also noted they would be monitoring the situation in the future and make necessary adjustments. Whether it means more players will join and servers would need to be expanded further, or merely a reduction in size after population leaves, remains to be seen.
Overall, the BF4 experience should serve as a good starting point for those looking forward to BF2042 but it's hard to imagine it can prepare you for everything.
Large Conquest maps support up to 64 players, only a half of what BF2042 can do and the older game doesn't have weather effects that completely change everyone's approach to everything.