To make do with = to manage with only
I really need 25 loaves of bread for the party, but I will have to make do with 20.
It appears that the ECB that they're talking about was not yet in existence when the piece was written. The Bank of France and the Bundesbank employed, at that time, 10,000 staff, but the ECB, when it opens, will only have 500 employees. "Will be" and "will have to make do" both refer to the future.
What was your problem with the use of the future tense here?
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