If there is a earlier hard-fork.
Will only the RingCT code be included in the version or every improvement until then?
Will this skip the March hard-fork or will the March fork use version 5?
From the Monero website:
Note that the v4 hard fork has been moved to the beginning of January, 2017, although the v5 hard fork remains set at September, 2017. This is to enable early availability of RingCT transactions on the Monero network, although they will not be enforced as the only possible transaction type until the v5 hard fork.
The hard fork in January 2017 will contain all the improvements for Monero up to that point, but the largest one by far will be RingCT.
There will be no March hard fork. The v5 hard fork will still be in September 2017.