I have my reservations too. Rumours according to Di Marzio is that it's only a 2 year contract, which I think is okay though. With him being 37 next year, I wouldn't be surprised to see us being in for a Haaland or another long term striker.
This year:
Rashford/Cristiano/Sancho-Cristiano/Cavani/Mason-Sancho/Mason/Cristiano
Next year:
Rashford/Sancho/Haaland-Haaland/Mason/Cristiano-Sancho/Mason/Haaland
Following year:
Rashford/Sancho-Haaland/Mason-Sancho/Mason
Looking at it...will we need Haaland if Mason continues developing as fast as he is? Just wondering if getting Haaland would impede Mason's growth. For the 3rd year, sure. But by then, he won't be available. Still, nothing to stop us getting another striker then.