The US 1000m record will never fall.
Basically too long for a 400/800 runner, too fast for a 1500 runner. No money in it for a 800/1500 runner. The honor of getting the toughest US record does not carry nearly so much weight these days.
Any 800m runner who has the speed will have to choose between a lucrative payday over 800m and relatively no pay for the AR record attempt at 1000m. Any 1500 runner will have to bypass a payday at 1500m for little payoff at 1000m. An 800/1500 runner will need perfect pacing, hard to get at 1000m.
The other deal breakers here is that the 800 WR and AR are falling so slowly, relatively few will come along with the capability of going after the US 1000m record because we average at most a <1:43 runner every decade or so.
Think of it this way: line up 8 or so of the all the all-time US greats from the past 40 years: Wholhuter, Robinson, Marshall Gray, Mack Symmonds, Solomon Wheating, Manzano Kenah, Jock Webb all at their bests for an 800m race. Who wins?