I dont think Elbaf will be the arc where Usopp's dream is accomplished but it could be tied around him in many ways.
While Nika will have a lot of focus, what a surprise, it doesn't stop Usopp to have a lot of involvement in the same arc.
Take Wano for example, Luffy had nothing going on for him, not a single plot line was tied to him because they were all around Zoro.
Usopp can have similar involvement in Elbaf because Giants are to him what samurai were to Zoro.
Whether those plotlines will be abandoned for Usopp as they were for Zoro, who knows, probably.
His dream is probably achieved elsewhere, if my guess is correct, vs Imu.