Smith has always been super picky about sequels, has he done any other than MIB? I suppose Marvel Money could be very persuasive. I'd still like to see a 1960s period piece F4. But the Lost in the Past and Found in the present bit was done by Captain America (and sort of by Captain Marvel, but not in Universe so it doesn't count). As with all these you need to come up with a good excuse why they haven't been around. So they either have to be a new team, thus the origin story, yet again, or they have been out of commission for a long time, like lost in the Negative zone since 1960s, but very little time has passed for them.
They didn't really milk Caps Fish out of Water story for as much as they could have, so it might not be retreading too much.