For all of the employees that received options based on the inflated $10bn valuation, not a good problem to have.
This is the danger of VCs wanting everyone to be a unicorn, and structuring their firms around that mindset. I agree that a $5bn or $2bn company is fantastic. Until those with capital agree, however, founders are almost required to pitch a fantasy.
So even if money was raised at a 10bn valuation based on the expectation of future value, a 409(a) valuation would probably place the company at somewhere closer to 10-40% of that, which puts employees in a much better situation.
Employees granted options recently after the highest valuation financing would probably be completely underwater if the company is really worth $2b.
When common is equal to prefererd, you have a public stock price.