Collections left in your estate that are of significant monetary value can create financial challenges for your heirs. A recent article covers the issue in the New York Times titled "Financial Considerations for Collectors of Art, Antiques and the Esoteric."
If you choose to sell the collection before you pass away, then you are likely to face steep investment income taxes if the items in the collection are sold for more than you paid for them. In some places this can be as high as 45% or more when federal, state and municipality taxes are taken together.
Alternatively, if you decide to pass the collection to your heirs, then the value of the items in the collection will increase the overall assets in your estate, which itself could have estate tax implications.
It is also possible that your heirs might have no interest in keeping the collection.
Another possibility is to donate or lease the collection to a museum. If done properly, you can receive tax benefits for doing that. However, for many collections it can be difficult to find a museum that is interested in displaying the collections.
Speaking with an estate planning attorney is always a sound plan, especially as you decide how you want to handle a valuable collection.
Reference: New York Times (Nov. 27, 2015) "Financial Considerations for Collectors of Art, Antiques and the Esoteric