If he is on the decline, can't press like he used to, and misses a lot of chances, then why would you want him back? I'd rather have Firmino at the front, getting around 30 goals and pressing like mad, and I'd rather have Salah on the right, since he is probably now the superior player. On the left, we have Mane, whose pace is very important. I'd rather get someone young, quick and versatile who can do two out of Mane's, Salah's and Firmino's jobs.
For the record, Firmino has 24 goals from 44 games so far, while Suarez has 26 from the same number of games. This is despite the fact that Firmino is not a centre forward for us but something like a false 9. And he does all that pressing.
So unless Suarez doesn't mind being rotated...