No, I don't think that. I think if United knock £20m off Martial's asking price - making it £55m - and then we might have a deal for Toby at £40m ... because no club is ever going to offer £75m for Martial, but another club might well offer us more than £40m for Toby.
In the meantime, Toby is in the shop window at the WC and Martial isn't. So the clock is ticking: unless United make a deal soon the chances are Toby will impress in the WC and another club will strike a deal with Spurs. And that will leave United scrambling for an inferior CB from elsewhere at a higher price.