24 hrs: 50kI like the way you think! I too am very optimistic about the Model 3.
week: 100k
month: 200k
year: 500k
I'm going to explain my reasoning instead of just posting numbers.
By end of march there will be between 100k-150k Model S or X owners. They know there is no risk in giving Tesla a couple of thousand dollar/euro for a registration. This is even more true for people outside the USA: there will be (tens?) of thousands of model E produced before the the first one is delivered outside the USA, so there isn't even a risk of getting a car with child diseases. A fair amount of Tesla owners will want an extra car within 3 years, they know they need to register on day 1 to get their car within 3 years (My Model S hasn't been delivered yet, but I will reserve a Model 3 on day one because I have to replace my 16 year old Toyota Corolla in a couple of years). Add to this the people who want a Tesla but can't justify the price of an X or S, they will also register on day 1. Considering these 2 groups of buyers, 50k will probably be conservative.
Fast forward 1 week. By then it's in the news how many preordered model E's there are. Anyone hesitating will place their rgistration.
Witihin a month, lease companies will register cars by the hundreds or the thousands out of fear of not getting anything to lease within 2 years of release. (In my country, lease companies are already predicting that Model 3 will be a big hit with company lease cars because of the fiscal situation of EV cars).
After a month, most people registring will be people that still have some doubts or people that just heard about Tesla).