Let's get the FACTS straight.
The US dollar WILL NOT become illegal in Cuba.
What is happening is that Cuba is changing the usage of currency within Cuba.
All tourists must now use the Convertible Peso which has an exchange value of = to US $1.00. This is used in all the hard currency shops, hotels, restaurants etc.
There is also the Domestic Peso valued at approx 24 to the Dollar. However this domestic peso is for the use ONLY of Cubanos, not people from outside.
There will be a 10% surcharge on the conversion of any US dollars to the Convertible Peso. However, there will be NO SURCHARGE on any conversion of other world currencies such as the Pound, Swiss Franc, Canadian Dollar, Euro etc. Only American currency will be devalued, but will still be allowed to be used in Cuba if you want to pay the 10% devaluation. If not, simply use any of the other fine world currencies.
Frankly, it's about time the Cubans droppe the fast-fading US dollar in favor of other more stable world currencies.