Or it could just assume the AI has an unbounded utility function (or bounded very highly). An AI could guess it only has a 1 in 1/B chance of reaching DSA, but that the payoff from reaching this is 100B higher than defecting early. Since there are 100B stars in the galaxy, it seems likely that in a multipolar situation with decent diversity of AIs, some would fulfill this criteria and decide to gamble.
Or it could just assume the AI has an unbounded utility function (or bounded very highly). An AI could guess it only has a 1 in 1/B chance of reaching DSA, but that the payoff from reaching this is 100B higher than defecting early. Since there are 100B stars in the galaxy, it seems likely that in a multipolar situation with decent diversity of AIs, some would fulfill this criteria and decide to gamble.