I partly agree, but also think that words tend to be used and catch on and spread if they're functional. "OG" is shorter than saying original, is easily said (vs. "orig"), and probably as short as you could get since saying "O" probably wouldn't work. If they're now using the word on antiques roadshow to evaluate a sword, I doubt that sword collecting was influenced by hiphop. Also you could pretend that OG is taken from OriGinal. By now the word is close to being stripped from its original roots.
Other slang becomes mainstream pretty fast, I swear I've even seen someone on the news describe something as "sick" (and the popularity of poker, whether or not they invented the term, helped push it along a lot, because they say "sick hand" a lot... I don't know if Poker became big in the UK as it did in the US for about 5-10 years).
OVO is an acronym that only makes sense within a specific scene at a specific time (and maybe on a specific message board). I could be wrong but I'm guessing it won't catch on and be used for other things. Except for the name of the new cirque du soleil show, but I don't think they got that from here.