Welcome to this Forum David,
Brother aaj, made a good comment. Although much of the current world events, doesn't look like it will be that kind of futuristic rather fallout 3/4(game) (
https://www.instant-gaming.com/image...shot/755-4.jpg ) realism.
However, for the sake of science fiction, indeed, more sects will emerge if they are not enough this day and age. We know from hadith (naration from Prophet Muhammad (pbuh) ), that Islam will split in 73 sects, with only 1 going to paradise and 72 ending up in hell fire.
Islamophobia, well it is rather hard to answer this question, as this all rather is going towards WW3, instead of being able to make it to another planet. But if we would follow that path, i think beside we as Muslim indeed believe by then A LOT people would already have become Muslim by choice ..Islamophobia not really would exist. For the sake of argument if majority even would not be Muslim, Islamophobia would not exist, because the world heading for destruction can't be blamed on Muslims. When such large calamities would happen, everything else for us human beings will look as if it is not worth to even mention it. With little people left, people would rather form unity to build something instead of looking at what divides us. We for example would look at what caused the chaos and destruction of this planet and will make laws to not fall in the same habits, whatever those will be. So people would rather be punished for greed and steal because of greediness for example. Or not sharing some of their wealth when poverty is a fact and poor people should be supported with some part of your money. Much of those laws, already exist within Islam, to prevent society in to collapsing.
A good way to indicate them being Muslim is indeed clothing, but not necessarily that. Much the character it self. For example, if somebody would gossip he/she would defend the person who the gossip is all about. Saying typical Islamic things, like brother aaj said. Within Islam a lot of emphasis is put on good character. Being good to the neighbors (whatever the religion)(Hadith: the least harm a Muslim can do to his neighbor is having him smell the food your are cooking but not giving him anything), good to the parents. Greet people despite not knowing them. Treating animals with respect and dignity. If somebody would insult him, not insult back. Just be kind and leave. Not getting angry, be good to ones wife, don't look at other peoples wives or other women even though they are not married.
Speak the truth even if it would be against you (already in the Qur'an)
"
O you who have believed, be persistently standing firm in justice, witnesses for Allah , even if it be against yourselves or parents and relatives. Whether one is rich or poor, Allah is more worthy of both. So follow not [personal] inclination, lest you not be just. And if you distort [your testimony] or refuse [to give it], then indeed Allah is ever, with what you do, Acquainted." Qur'an 4:135