BF1 may have been the end on the uphill climb for Battlefield and we may be on the cusp of the downfall.
I hold little to no hope for BF5.
They will either re-introduce helicopters or they will not. I think they almost have to. For me personally, helicopters are the exact thing that ruins Battlefield. Planes are one-pass deals that have to turn around at high speeds. Helos can hover. That makes for a whole new dynamic.
I know this: I used to play with a guy who was so good with his Helo in BF3 that no 2 SAMs could take him down. You needed 3 SAMs working together to bring this ONE pilot down.
I'll give the guy credit, he was very good with that helicopter. He was also a funny and likable guy, but he absolutely highlighted what was wrong with the balance in all of the 'modern' BF games. Helicopters. They are categorically 'not fun' for people who like to play infantry. Gun-Play in Battlefield is actually really good and has been since BF3. But that's why being Helo'd from above while in a gun-fight on the ground is so damn infuriating. It's why I left BF3 and never bothered to purchase BF4. If they go back to that whole model again they will have lost me once again and for the same reasons.
BF1 is/was the best BF game ever made. I'm not sure they can top this effort easily.