@lifofifo on X created an onchain futures contract for BIP 444.

Because BIP 444 proposes a soft fork that makes certain kinds of tapscript unspendable, it's not too hard to set up a 2 of 2 multisig that has two mutually exclusive spending paths, one of which relies on the kind of scripts BIP 444 proposes making invalid. Both sides of the bet presign transactions with a locktime after the proposed activation date.

Not only is there a setup for this kind of contract available:

But, it seems that some people are already putting their money where their mouth is on activation of the reduce data temporary soft fork.