It will have been 2 years since BF3 came out if BF4 comes out during fall (it will). That's pretty good compared to CoD and a miracle for Battlefield. What did people expect? Not to see one for whole 5-7 years?
They are doing the same thing as COD, but with two brands instead of one.
Infinity Ward was Even, Trench was Odd.
Battlefield will be every odd year, MoH will be even.