What happens to my spouse with dementia if I get Covid and have to be hospitalized?

If you become ill enough to be hospitalized and have no friends or family to let know in an emergency then basically the ambulance that takes YOU in is followed by another getting your hubby. We OFTEN had this in my career as a nurse. The spouse would be hospitalized briefly while respite or facility care was arranged during your acute admission. So upon entry to hospital you notify social services.
Do know that WHEREVER you go and WHATEVER you do the notification in your wallet must be there to say you have an ill spouse at home who needs IMMEDIATE assistance. We in ER saw that, and saw it even for PETS, and pet services were rendered by our Animal Care and Control.

LB
You could contact your Area Agency on Aging and ask for a needs assessment for your husband. No need to wait for COVID. Having your information in their system might help in time of emergency. Each county has an Area Agency on Aging. Look for their website.
You could also ask your husbands doctor if he would qualify for home health. This would give you help with your husband now.

APS would be called, and the state would step in and take emergency guardianship of him.