The Black Widow Funko Pop from Avengers Endgame will likely soon be vaulted because distributors have quit taking orders for this Pop. The demand is over 3x higher than the current supply on Ebay which is typically a good sign that the Pop will increase in value. There are currently only 2 sellers left in stock on Amazon.
With the new Black Widow movie hitting theaters on July 9th, the demand for this Pop will only go up. There is an Entertainment Earth exclusive of this Pop as well that comes with some Pop trading cards. If you are a Black Widow fan this would be a great time to add this one to your collection.
Of course, this is speculation and not investment advise. Let me know if you agree or disagree in the comments below and feel free to mention any Pops you think are set to pop in price as well!