Best case scenario, both games will do well and be well received. As for Horizon overshadowing Zelda...not sure if that can be possible. It's not out of the realm of possibility, mind you, but when you had countless people running to get in line for Zelda BoTW's first demo at E3 and still have that type of crowd during these latest Switch events, plus, have the latest trailer be received so positively, the game's not likely to step aside without a fight.
Plus it's Zelda, a 30 year old franchise that has had timeless classics that very few could match and that many could only dream of matching. This is also Zelda going back to its NES roots when it redefined the adventure genre back in 1986-87, which is something most, if not all, long time fans have hoped for.
Horizon will probably do fine and it appears to have good things going for it as a new IP. I'm just not going that far in thinking that it can overshadow something like Zelda.







