I don't understand why you expect a 5kwh bump every year when it took tesla 3 years for the first 5kwh increase.
I say that because Elon Musk and JB Straubel have given guidance repeatedly that there will be a 5-10% increase per year between now and 2020 due to advances they are currently seeing and expect at the gigafactory in Nevada.
They are telling press, investors, industry analysts, etcetera to expect this.
They did not say that in the far past. They did start saying that more recently. When exactly the transition was I didn't try to pin down. I just pay attention to their guidance. I suggest reading
Tesla Gigafactory Investor Thread
Tesla Gigafactory
until you find the links to the videos of Musk or JB being interviewed or giving a live presentation at a conference. You'll see several references to the coming capacity increases in slides and verbally.
At the conference for just after the 90 kWh release Musk said that there would be an increase every year or some wording similar to that but said it wouldn't be worth buying a new battery for a used car until at least 2 or 3 years worth of capacity improvements had occurred (implying wait as long as you can between pack upgrades because we'll be upgrading packs more often than it make sense for you to do so).
I'm going totally from memory but if you really need me to I can cite references and post more accurate quotes some day when I get bored.
Beyond that I'm just using round 5kw numbers because its easier to guess that. They could possibly skip a 5 and make a 10 jump or use odd numbers. I don't have insider information on specific capacities or release dates.
I'd also expect the low and high packs to increase on seperate months or even separate years as they run out of old production and start using new. The fact that they'll be upping the low and the high means they may do one in early 2016 and the other in late 2016. I doubt that they'll bump both at the exact same time.
Oh and we currently have
low = 70
mid = 85
high = 90
I'm expecting the mid is a phase out of the old high and once they run out of 85s or want to introduce a 95 the 85 will disappear. I won't guarantee that they'll always keep more than 2 sizes available in new cars. I won't rule out that for very very short periods there might be 3 or 4 pack sizes as they phase in a new capacity for the new low, new high, or both.