After this big influx of DD which completes the X-Lines specification for the routes apart from the coaches for the X9/10 i cant see anymore DD routes getting new buses soon, any upgrades from newer buses are most likely be from cascades from elsewhere, single deck vehicles is the only logical next part for investment to replace the older not so eco friendly vehicles allowing them to be withdrawn/sold, this will probably be a long process over a few years as there will be no big hurry to spend millions on new vehicles at present but i would be surprised if anything other than MMC200s was ordered