Impossible to say.

The MSY-LHR route is the only non-stop to Europe from that airport, so it's quite likely that there will be a high proportion of connecting passengers. Some of those at least are likely to miss their connections and be rerouted. Others may cancel voluntarily, e.g., due to the strike.

You may also be able to reroute via ORD, DFW, and I think MIA with possible compensation.

An aircraft swap is also a possibility but it won't be plugged in yet.

A downgrade is also possible, and the compensation for this is quite generous (and the WTP experience is reasonable on a day flight). However, I'd say that's still not a particularly likely outcome in view of all the other, more favourable options above.