Will there still be skateboarders?
Yes.
Will skateboarding be outlawed all over the world then?
Moreso than it is now?
Will it be a jock sport with guys training hard for the Olympics?
If we let it happen, there will probably, eventually be a jock-minded version of skateboarding that exists outside of skateboarding as we know it.
Will we look at Fully Flared like we look at The Search for Animal Chin now?
Probably not, but it'll be one of those highly regarded vids like H-Street's Hocus Pocus or something similar. Gotta keep in mind that a lot of videos are going to come out between now and then, and skating's video history just isn't that long. Animal Chin will be on a pedestal forever in large part because of it's age, some of the (then) revolutionary things filmed (and the way they were filmed) as well as the cult status.
Will Nyjah Huston still be pro in 2050?
Not unless they have a master's handrail contest on ESPN. I like to think he'll make it big again, buy Element out of spite, then run it into the ground based off of his elderly dad's business advice.
Will it still be possible to do a ground breaking videopart?
Too subjective to answer with authority, but I'll probably always trip out on new footy.
Will there be new tricks or terrain?
Yes, and hell yes. Evolution!