Honestly I think 5.XX Summoner has everything it needs as far as a tool set, just needs to be worked to mesh better.

People have responded positively to how Firebird trance and Demi-Phoenix work so I would expect DWT and DBahamut to redesigned to work similar.

I would expect Summon II, the tank Egi to be dropped all together since this has been the slowly happening since 4.0

I would believe the next evolution of Summoner would be one and done summons were as you call it, effect happens, and it goes away. Whether that method is built up, channeled, or just a normal cast/cooldown is another discussion.