I would be very disappointed if Keldeo dropped to A- rank. people seem to be missing out on the reality of what has happened to and for Keldeo this generation, and I think the lack of rain is being blown a bit out of proportion.
If we look at Keldeo last gen, it was a very capable and powerful Pokemon that thrived on wearing down the common water resists and sweeping late-game, usually with its Scarf set. Pursuit Pokemon such as Tyranitar for Sand teams and Scizor for rain were good pairs for trapping Lati@s, Celebi, and Jellicent to allow Keldeo to clean up a team once these Pokemon were weakened/eliminated.
In XY, Keldeo got three major nerfs: rain lasting only five turns, Hidden Power being lowered to 60 Base Power, and Flying priority. However, I believe that the metagame has shifted in a way that makes Keldeo just as good as it was last generation, only in a different way. Keldeo is no longer the late-game cleaner it was in BW; instead, Keldeo should be seen more as a powerful wallbreaker with Specs or setup sweeper with Calm Mind. Scarf is almost nowhere to be seen. And that's because Scarf isn't a great item right now, which is actually good for Keldeo! Now it can run its Specs set without having to worry about being outsped next turn by a Scarf Thundurus-T. It has the freedom to spam Specs Scalds, which not only hurt, but also have the ability to burn the opponent. Furthermore, Keldeo's more common checks from BW are by and large gone from the metagame with the exception of Lati@s. While it did gain a few in Talonflame, Pinsir, and Azumarill, these are more offensive checks, and none can 100% switch into Keldeo the way that Celebi or Jellicent could (Mega Venusaur can, but it is very prepared for in this meta and even it doesn't like being burned by Scald!). While this does mean it's easier to revenge kill Keldeo, it also makes Keldeo's moves much more spammable, as not every team carries a dedicated Water resist (Rotom-W is mostly physical and takes a crap ton from Specs Hydro or Secret Sword). Not to mention, in a generation where Dark moves are a lot better, and Bisharp is one of the best Pokemon on HO, Keldeo being a great check to it in addition to everything else makes it a great choice for offensive teams.
Another positive for Keldeo this gen was the addition of Aegislash and Landorus coming down from ubers. Aegislash is a fantastic Pursuit user, and as we all know, Keldeo and Landorus + Pursuit user is a very dangerous combination. Aegislash also checks some of the Pokemon that beat Keldeo, such as Mega Venusaur, Azumarill, Mega Pinsir, etc. (please note that I said CHECKS, not counters).
I feel that Keldeo more than deserves its place in A rank.