Most gamemodes will be implemented into 1.8...
Some problems are:
-Some maps may not be included due to new Blocks.
-Some features could be removed due the Difference between 1.8 - 1.9.
Games such as FFA Elytra, Minerware, Blockband etc. could probably not be implemented.
Anyway more games are going to be implemented.
"Patience is the Key" for now....