Does this mean the virus has peaked across the world? In that there are enough people in the general population who now have antibodies?
If everybody everywhere was living life as normal, mixing, travelling etc, then it might mean that. But as long as there are masks and travel restrictions and 2m distancing to any great extent, then no. The virus is merely being suppressed to varying degrees.
If a virus mutates enough times is there not also a chance for it to become weaker in the long run? I understand it can go the other way however coronavirus seems like a virus which doesn’t necessarily want to kill its host unlike Ebola
There is a chance it could mutate to become weaker, but that will only happen if it confers an advantage to the virus. With Covid, because it can spread well before the host becomes ill, there is no particular advantage to it in becoming weaker. Viruses don’t actually ‘want’ anything, they are not sentient. They mutate as a matter of course, and any mutation which enables it to spread faster/wider will be selected for and become more frequent.
Is there a possibility this could become a dominant strain of flu going forward?
No, because it isn’t flu. Theoretically it could outcompete flu and become more prevalent than it. For instance, there has been very little flu this year, because the measures which have been somewhat effective against Covid have been highly effective against flu. I suppose it’s possible that if we keep it up for long enough then flu could become extinct, but it seems unlikely. More likely once Covid vaccination is sufficiently widespread that we all start mixing again, flu will stage a comeback.