Personally, I loved the seasons in generation V.
They added further replay value (the main one was the sheer number of new pokemon to try out and build your team with), since they only changed once per month.
Similar to the day/night-cycle it's a really nice touch that makes the region feel more alive.
Unfortunately, just like with the absence of the daily cycle in generation III (just after being introduced the generation before), the seasons have not returned for generation VI.
If you've travelled through Kalos in XY, you probably noticed 2 things regarding seasons:
- well, there aren't any obviously. The places are all aesthetically/thematically locked, like in every game besides BW/BW2
- there is parts of Kalos that feel like they embody a specific season nonetheless
And upon closer inspection, they even seem to be oriented in correct order, going clockwise around the region, just like the general progress of the story is headed.
Of course there is exceptions (the most summer-like town is probably Kiloude in the far south, and Snowbelle likely being snowy only due to the Abomasnows living there rather than the climate), but overall it is an interesting case nonetheless.
It makes me wonder... what if seasons were actually planned to be in XY, but put aside in order to hold the visual diversity of the region in place for the initial gen VI games? And if they were, could it be that this is something Gamefreak intended to deal with properly for the sequels, when they have time for details like these?
Their forms being dependant on seasons, Deerling and Sawsbucks got completely ignored too of course, but they could have been retconned to work like the Burmy forms if Kalos is meant to be fixed this way (so finishing a battle in the snowy places would change it to its Winter-form)... the fact they weren't handled this way could be a hint that Kalos is getting seasons in the sequels though.
However, given that this would be quite a bit of work for a rather minor and mostly aesthetical feature, the more realistic expectation is that we won't be seeing the season mechanic again for now (and if it means the developing time will be well spent on other things, like a whole new second half of the region popping up, or an amazing Battle Frontier etc., it will barely bother anyone).
But if they did decide to go down that route, reintroducing seasons in follow-up games could become a tradition, and a permanent solution to the unclear future of this game-mechanic.