Is this to improve the dev experience of legacy systems or actually launch new mainframes? What is the market for new mainframes? I'm guessing scientific number

Is this to improve the dev experience of legacy systems or actually launch new mainframes? What is the market for new mainframes? I'm guessing scientific number crunching/modelling that can't be parallelised well? For someone who has never touched a mainframe I have no idea what to make of this!