In the last 3 years, as you said... 3 and 3 assists last season (514 mins - 5 starts), 3 and 1 assist the season before that (769 mins - 7 starts) and 11 and 2 assists before that (1460 mins - 17 starts).
Solanke 1 and 1 assist (619 mins - 5 starts).
I looked it up and he got 2 last season (I was talking about league goals but understand if I wasn't specific enough about it). One as a sub against Arsenal, one starting against Huddersfield. The 3rd is him coming on as a sub and scoring in the 7-0 against Maribor.
Anyway I think that given that Solanke is clearly developing and improving, and Sturridge's body is less equipped to play the Firmino role, it's not exactly an outlandish statement to suggest he should (and I expect would) be ahead of Sturridge in the queue for the West Ham game.
Last season both of them scored one goal in games they started. In the five games that Sturridge started last year, we only scored more than one goal as a team in one of them (Huddersfield, 3-0), so it's not like the team suddenly leaps up in goal threat with him playing.