I'm imposed under French laws but I have the same concerns.
With Covid 19, it's likely that the rich will taxed to contribute. Macron killed the wealth tax on financial assets (ISF) and introduced a 30% flat-tax on all capital gains/revenues (PFU), so billionaires' wealth has risen much more than in the US. People will realize that sooner or later and demand some tax hike. Also, any US policy change should influence on the other side of the Atlantic because the politicians keep arguing that they cannot raise taxes because the rich would flee to the US (or some tax heavens where people don't really intend to move, IMO).
Anyway, I've bought ~5,000 shares since 2012 at an average post-split price of ~$50, sold them all at $100 in mid-March and bought them back at $90.
My taxes on realized gains amounts to $75K assuming the flat tax will apply (they'll be due in end of Q3 2021). At today's prices, I have 1.85M of unrealized gains, which would cost at least $555K in tax.
I'm not sure when the tax rate becomes definitive, so I don't know if selling everything again would secure the 30% rate on all gains ($2M incl. unrealized). My understanding is that I'd benefit from this only I can buy them back at X% below the selling price (where X is the difference btw the current and future tax rate).
I intend to hold the shares for the long term, so maybe I shouldn't touch them (whatever the changes in taxation) because one can't preclude the possibility that Tesla will pay dividend in a decade or more, at which point I'd finally profit on the shares not sold (to pay taxes).
Does that make sense?