As far as I know, Coinbase is not using SegWit. Wouldn't SegWit allow em to spend less on transaction fees?
Coinbase has been delaying segwit for ages now.
There are alternatives to Coinbase, they'll lose customers to those eventually
Now, I think I may give him the benefit of the doubt on delaying segwit until at least May, because Bitcoin Core 0.16 does not come out until May and this will be the version that supports bech32, so they may be waiting until then, im myself waiting until then to use segwit at all.
Should be far earlier than May. Some features have been moved to 17.0 so that 16.0 can be centered around Segwit wallet and bech32.
I would guess March is more likely the release date for 16.0