Based on what you said earlier my guess is you believe there is too much risk to bet on Tesla achieving this growth rate. I can identify 5 categories:
1) Demand - addressed above
2) Competitive - another long topic, but unless you consider the Bolt a threat the earliest we will see a potentially credible competitor is in 2018 with the Audi Q6, followed by Mercedes in 2019 and BMW in 2021. Plus there is the long distance charging infrastructure issue for all of them
-- Bolt is planned for 30K/year and limited to 90K/year without building a second factory (which will take 2 years and hasn't started)
-- Audi is targeting the Model S price range and again appears to be limited to ~50K/year
-- Mercedes and BMW also appear to be targeting the Model S price range and limited to ~50K/year
In short, I don't see competition for Model 3 coming along before late 2019 (if GM starts building a second Bolt factory in January) -- more likely 2020. Even if the charging infrastructure is solved.
Hyundai Ioniq is a potential "competitor" when it gets its 200-mile range version -- promised in 2018, but may slip to 2019 -- *if* they get long-distance charging *and* build enough of them. I couldn't find production numbers, but I found some references saying they were "expecting" 77,000 sales in 2017, so again, production capacity is probably too low.
Nissan Leaf 2.0 with the larger battery is a potential competitor when it eventually comes out (supposedly 2017), *if* they get long-distance charging (which is more plausible for Nissan than for anyone else) *and* build enough of them. Nissan is certainly the most likely to actually have volume production, since they can already produce at least 300K/year (at four factories).
I believe the total demand for electric cars is so high that almost all of these cars will be displacing ICE car sales, however.
If there were multiple competitors planning to produce 500K/year, I might worry. Instead, it looks like the sum total of all "competitors" other than Nissan is under 250K/year, and even then only in 2019 or 2020. On top of this, most of the competitors are limited by their battery suppliers' capacity. Nissan has a captive battery supplier, but none of the others do, and Nissan is talking about selling it (!?!?)
BYD is a wild card but seems to be focusing on buses and trucks in the international market, which is great, and keeps them out of direct competition with Tesla everywhere but China.
3) Availability of capital - definitely a risk, hasn't been an issue in the past and it appears that Wheeler/Musk are de-risking here with more prudent management of capital and OCF growing now that they are at a 100K annual delivery rate.
I don't think this is a risk. I do think they'll rely heavily on loans (not stock issuance) prior to the mass production of Model 3, so that means *sudden large interest rate rises* are a risk which could hurt profits.
4) Execution - This is the big one. We will know in 12 months.
Yeah, they've become very tight-lipped about this but I personally see no reason to worry. The only reason others have identified is that they haven't seen Model 3 being test-driven on streets, but I strongly suspect they'll do their tests indoors anyway.