I happen to know from previous interviews that some of the current egis will be altered gameplay-wise so each egi can adapt to varying situations, so Ifrit will become more than JUST a melee DPS and Garuda will become more than JUST a ranged DPS, then Ramuh and Leviathan egis will fit in there somewhere.

As for appearances... what kind of appearances are you suggesting? I mean, what won't happen is individual summoners getting full-sized summonable versions of the primals. Whether or not the devs are still going to let FCs summon Primals is up in the air, but no individual summoner will get that power.