While it is very difficult to project future profits to begin with, there are certain firms other than banks that can project the future profits of another firm more accurately. For instance, a large assembler to a certain extent knows the sales figures of its suppliers. The simple reason is that the assembler procures orders from the supplier.
The lack of convergence in key macroeconomic variables may suggest that the region is not yet ready for a common currency. However, I must add that it may not be crucial to meet all the criteria prior to the formation of a union.