I am not quite sure what you mean between your question and your statement. But our current assessment of the severity is most likely due to the co-morbid problems and the patient's age. So diabetes. obesity, hypertension, asthma, COPD, heart disease, immune problems, etc. all increase the likelihood of a serious episode. The chance of a virus mutating to a viable virus, in any one individual is currently estimated to be about one in a million, so not very likely in your case. Of ,those viable mutations, they can be either less or more pathogenic. The infectivity factor, the number of virions required to cause an infection is estimated to be at least a hundred. Usually there are millions of viruses, or more in an infection, these are all trying to infect and reproduce. The fact that one of these viruses mutates, does not mean that it is this exact mutation and not one of the other millions of virions that spreads the infection. So, the odds for any one individual are very slim.

Some research says possible

Yes, it's possible according to findings and of course it will be varied from person to person.

To my understanding, there are two different mechanisms of alterations in genetic material of living organism. First one is the long-term genetic evolution mostly induced by the variation in climate and food availability while second comes with very short-term mutations induced by several intrinsic and extrinsic factors.

In case of SARS-CoV-2, the different identified variants are due to host adapted short-term mutations. It may cause a trouble in vaccine development if the genome is changing very quickly.

Clearly the manifestations depend on the characteristics of each individual. I think it is unlikely that the virus will change in the passage.