The fintech company still faces a lot of challenges.Block's (SQ 2.52%) stock has shed three quarters of its value during the past three years. The fintech stock was a market darling in 2021, but its luster faded as growth cooled and rising interest rates hurt its valuations.Let's take a fresh look at Block to see if its shares will head higher or lower over the next three years.An evolving business modelBlock splits its fintech business into two ecosystems: Square and the Cash App. Square provides digital p ...