Why upgrades only on 320? Because some arrogant and short sighted (locals apparently) people complained because they don't have the hours to do get 330 command, but they couldn't see that if they had continued the 330 upgrade they will be captains faster....
Yes they will start conducting interviews on may(be), but a lot of people already selected has 30 + guys on top so that counts for an extra year on top of your 3 years, in less than 4 years? not a reality.