I believe that the Board will work very hard to make the new stadium a reality as it is the only way that they can make a substantial profit on their investments. If Moshiri is here only for the profit, the club will be sold, not long after the stadium is opened, assuming a buyer can be found.
The £300m loan, though, is not enough to build a 60,000 seat stadium. Spurs new stadium is reported to be costing £750m for 61,000 seats. The cost is inflated, firstly, because it's in London and, and secondly, because of the NFL link which requires two different fields of play. Also building costs have risen because of the rising costs of raw materials, falling pound etc.