A new joiner now will have to plan on a minimum of 8 years before upgrading. Emirates has grown rapidly doubling the fleet every few years the upgrades have come thick and fast which was great for the people who joined at that time.
The upgrades you are seeing now on the 777 at the 4 year mark are as a result of that rapid growth. It's no use to look at the orders and think they are additional airframes the fact is the A330/340 fleet will be retired over the next 3 years along with the old 777-200 and 777-300 which means the gain of aircraft is going to be relatively small.
Emirates is not the airline if you are looking for a quick command....those days are gone. It's still a good option if you are young and single but a married guy with kids really needs to think long and hard with the way prices are moving.