For him becoming Andor's new bestie we may have to wait and see in the next time jump how that pans out. We the audience know he's a useful asset but I'm assuming by episode ten the characters won't be that trusting yet.
Even in R1, Cassian still didn't fully trust him; he wouldn't let him have a gun.
Personally, I'm more interested in seeing more of the rebellion and other rebels we haven't met yet on Yavin IV, but in particular, a view of the wider rebellion as such as opposed to someone in particular. Especially now that Andor will have hopefully emancipated himself from Luthen, and the organisation is kicking in. It only makes sense this includes Nemik's manifesto making rounds in it, since it would be a weird thread to abandon if they referenced the “rebellions are built on hope” from Rogue One, so now in effect Rogue One back-references words that are more minor in both the show, and Andor's life, and given that Vel is also with us as one of the Aldhani rebels, and she's close to the to-be leader of the rebels.
I'm thinking that, in retrospect, Rogue One will be a microcosm of Cassian's entire life seen through a kaleidoscope. Not just the scene I always talk about where him learning about Marva's passing visually echoes his own death scene, but, for instance, the escape from Narkena 5, where he had to climb no matter what, and he has to climb through the archives to the transmitter tower on Scarif. It'll be interesting to see that whole thing in-context (which is why I'm desperately hoping there isn't any kind of distant epilogue next week; as far as I'm concerned, R1 must be able to slot in cleanly as the fifth arc of season 2).