I very much doubt that Stansted will see an influx on new or more cargo movements more a strike at Heathrow. BA’s main cargo airline is themselves with Bell Freight and DHL.
DHL already have a big operation at East Midlands and a substantial presence at Luton.
Im my eyes the most likely change could be Qatar who operates their flights for BA Cargo. With Freight from Hong Kong. They may do an extra flight but this time of year an extra flight from Qatar isn’t unusual.
Im not saying it’s impossible Stansted might see the odd extra flight but it’s highly unlikely. Never had big changes before on previous strikes from other UK cargo hubs.