I believe there'll be a fourth wave, but perhaps more regionally.  The 1918 influenza pandemic lasted from Feb '18 till April '20.  We're just a year into this one.    
Way too many stupid people in this country.  Starting with governors.  Then with vaccine deniers.  I'm embarrassed to say that up to a third of healthcare workers are refusing the vaccine, including hospital employees and home care workers.  Plus, we have all the new, more virulent variants.  
I suspect we'll be needing "booster" vaccines for years to come.  
We'll shortly have a surplus of vaccines.  Will he help less fortunate countries???