Considering how much work and effort it took to get SR to look like it is now... I'd say that, that is a long time away even for those game modes.
The one that needs it the most is Dominion. Think about it. Dominion was kind of based off the Institute of War. If anything, it now seems to be out of place. I would love for it to be remade into a Piltover or Shurima feel. The scenery just doesn't seem as grand as the others. (SR seems like its from Ionia.) Also, Dominions minions don't do much. They don't work as well as even Twisted Treeline's minions. (That's pretty sad.) The turrets can deal damage, but why do they stop when being captured? That defeats a purpose and makes it too easy for my taste. It would be much more rewarding for the enemy (sorry to say, but also for us) if they dealt damage and were able to stop a capture. Also, why not make it so that a captured location doesn't stay captured for more than a specific amount of time? It would make {{summoner:17}} seem all the more needed and useful. And lastly, it might be fun to see a Ranked version of Dominion. The Crystal Scar might be a cool place in Runeterra.
Twisted Treeline doesn't seem that bad in a state (compared to the Crystal Scar) and I feel that's because its based roughly on Summoner's Rift. The minions move, act, and are well programed. So are the turrets (which all got updated looks and a added one down bot). The buffs from the... buff area? I don't know what its called... They got changed. And I think Vilemaw even got some changes. In general, there's more on Twisted Treeline to do than on Summoner's Rift. The only update I'd even think of is a more eerie feel (as in purple fog, ghosts that appear out of nowhere and attack, stuff like that to make it more haunting). The real thing Twisted Treeline could use is a draft pick, or something along those lines. Dominion has one so it just seems fair.
Lastly, I'm hoping they decide on bringing back Butcher's Bridge because thats a waist if its just a event thing. I mean, its a whole new map. What's the point if its just for events. It makes me not care as much to play if I have to say "goodbye" after a few days and feel sad about it. Its not a (URF, Ascension, Doom Bot) game mode. Its a new map for ARAM that had A LOT of work put into it. I'd really like a new map (even though I do like the original better) because there really was a lot of work.
I also must say that a new turret system should be made for each. Crystal Scar's just needs a updated look. Twisted Treeline could have brick towers that have ghouls that send out plasma blasts to go along with how the Shadow Isles are to feel. And Howling Abyss... I'm not sure really. The guys at Riot might have some good ideas.
But when they can make SR actually look and feel like this picture:
http://gameinfo.na.leagueoflegends.com/en/game-info/game-modes/summoners-rift/
I have great, high, and happy expectations they can follow with these:
http://gameinfo.na.leagueoflegends.com/en/game-info/game-modes/the-twisted-treeline/
Like I said, Twisted Treeline seems sort of fine at the moment... It follows this look very closely. But the image is also the reason I asked for purple fog.
http://gameinfo.na.leagueoflegends.com/en/game-info/game-modes/howling-abyss
Still going to say the art in this mode is the best (under SR) even if the image is better than the map. I even prefer this map over Butcher's Bridge but would like the map back since I also like Bilgewater a lot. (And the map was seriously well made.)
http://gameinfo.na.leagueoflegends.com/en/game-info/game-modes/the-crystal-scar
Look at this picture, then at the map... You can tell there is now room for improvement.
Sorry this was a long comment, so:
TL;DR
Crystal Scar needs a update the most. Each one could be updated a little to help each one not grow stale. I want Butcher's Bridge to come back. Hope Riot fixes Crystal Scar's bugs and updates it to either a more Shuriman or Piltover feel.