They should be collecting signatures from employees at xAI. I think they're probably most likely to fill the space left by Anthropic.
I think what is much more interesting is what OpenAI and Google will do. There's probably some threshold of signatories where the companies in question do not fire everyone when they decide they want the DoD's business, the question will be how many people have to sign to cross it... and will enough people sign.
I don't think Google would bat an eye at firing 500 people to secure a DoD contract, but would they fire 5,000?
xAI is a pure choice. Their people have the ability to work at Anthropic but choose xAI.
(I dropped out at the end because there were issues with HR not wanting to hire in certain geos, and me not wanting to relocate to the USA or London)