If Isaiah didn't fail the physical the deal should be a go.Why are you so fixated on him being lost for the season?
If he's more seriously injured than Cleveland was lead to believe, he's less valuable, and they should get more coming back.
My guess is they'll come to some resolution here, and i know you're coming at this from a Boston POV, but Cleveland has a point here.
If he failed the physical then cancel the trade.
The regular season is pointless. If Isaiah isn't out for the year he will help Cleveland win the East. They could be the 8 seed they are winning the East. Thus the only concern should be if IT can't play. If is just going to be out some time then this all about extortion.